UNIVERSITY  OF  CALIFORNIA 

ANDREW 

SMITH 

HALLIDIE: 


The  Publishers  and  the  Author  will  be  grateful  to 
ar.y  of  the  readers  of  this  volume  who  will  kindly  call 
their  attention  to  any  errors  of  omission  or  of  commis- 
sion that  they  may  find  therein.  It  is  intended  to  make 
our  publications  standard  works  of  study  and  reference, 
and,  to  that  end,  the  greatest  accuracy  is  sought.  It 
rarely  happens  that  the  early  editions  of  works  of  any 
size  are  free  from  errors ;  but  it  is  the  endeavor  of  the 
Publishers  to  have  them  removed  immediately  upon  being 
discovered,  and  it  is  therefore  desired  that  the  Author 
may  be  aided  in  his  task  of  revision,  from  time  to  time, 
by  the  kindly  criticism  of  his  readers. 

JOHN  WILEY  &  SO^S. 
43  &  45  EAST  NINETEENTH  STREET. 


STEAM-BOILER 


EXPLOSIONS 


IN   THEORY   AND  IN   PRACTICE. 


BY 


R.  H.  THURSTON,  LL.D.,  DR.  ENG'G, 

DIRECTOR    OF   SIBLEY    COLLEGE,    CORNELL    UNIVERSITY;     OFFICIER    DE    L'lNSTRUCTION 
PUBLIQUE    DE    FRANCE;    PAST    PRESIDENT    AM.  SOC.  MECH.  ENG*RS  J    FORMERLY 
OF  U.  S.  N.  ENGINEERS ;      AUTHOR    OF    A     HISTORY     OF    THE    STEAM-EN- 
GINE,    A     MANUAL     OF    THE     STEAM-ENGINE,     A     MANUAL     OF 
STEAM-BOILERS,    ETC.,    ETC.,    ETC. 


^THE1 

.3!' 

;  ^o;s\\K 


XUustratefc. 


THIRD    EDITION. 
SECOND    THOUSAND. 


NEW   YORK: 

JOHN  WILEY   &  SONS. 

LONDON:    CHAPMAN  &  HALL,    LIMITED. 

1903. 


COPYRIGHT,  1887,  1903,  BY  ROBERT    H.   THURSTON. 


PREFACE. 


THIS  little  treatise  on  Steam-Boiler  Explosions  had  its 
origin  in  the  following  circumstances  : 

In  the  year  1872  the  Author  received  from  the  Secretary 
of  the  Treasury  of  the  United  States  a  communication  in 
which  he  was  requested  to  prepare,  for  the  use  of  the 
Treasury  Department,  a  report  on  the  causes  and  the  con- 
ditions leading  to  the  explosions  of  steam-boilers,  and 
began  the  preparation  of  such  a  report,  in  which  he  pro- 
posed to  incorporate  the  facts  to  be  here  presented. 

The  pressure  of  more  imperative  duties  became  so 
heavy,  immediately  after  the  receipt  of  that  request,  that 
the  work  was  interrupted  before  it  had  been  more  than 
fairly  begun.  An  examination  had  been  made  of  the 
records  of  earlier  legislation,  in  the  United  States  and  in 
foreign  countries,  relating  to  the  regulation  of  the  use  of 
steam  boilers  ;  and  an  investigation  was  begun  tracing  the 
experimental  and  scientific  development  of  the  later  the- 
ories of  explosion.  The  work  was  never  entirely  given  up? 
however,  and  the  notes  collected  from  time  to  time  were 
added  to  those  then  obtained,  and  have  since  formed  the 
basis  of  later  lectures  by  the  Author  on  this  subject. 

In  the  year  1875,  the  Author,  then  a  member  of  a  com- 
mission formed  by  the  government  to  investigate  the  sub- 
ject, was  asked  by  the  Cabinet  officer  having  direction  of 


116603 


jv  PREFACE. 

the  matter  to  accept  the  chairmanship  of  the  commission 
and  to  give  his  time  to  the  subject  under  investigation. 
For  sufficient  reasons  he  was  unwilling  to  undertake  the 
work,  and  an  older  and  wiser  head  was  appointed.  His 
connection  with  that  commission,  however,  further  stimu- 
lated that  interest  which  he  had  always  felt  in  the  matter, 
and  led  to  the  study  of  the  subject  from  new  standpoints. 
It  seemed  evident,  from  what  was  learned  there  and  else- 
where, in  the  experimental  explosion  of  steam-boilers,  that, 
usually,  the  only  unknown  element  in  such  cases  was  the 
magnitude  of  the  stock  of  energy  stored  in  a  boiler  before 
explosion,  and  the  extent  to  which  it  was  applied,  at  the 
instant  of  the  catastrophe,  to  the  production  of  disastrous 
effects. 

The  calculation  of  the  quantity  of  energy  stored  and 
available  was  undertaken  and  partly  completed,  and  then 
was  interrupted  by  the  decease  of  a  most  efficient  and  help- 
ful assistant ;  was  again  undertaken,  later,  by  two  earnest 
friends  and  pupils  of  the  Author,  and  was  finally  completed 
in  the  form  in  which  it  will  be  found  presented  in  the  fol- 
lowing pages. 

Thus,  the  subject  is  one  which  the  Author  has  endeavored 
at  several  different  periods  in  the  course  of  his  work  to 
take  up  and  reduce,  if  possible,  to  a  consistent  theoretical 
and  practically  applicable  form.  On  each  occasion  his 
labors  were  interrupted  before  they  were  fairly  begun. 
It  cannot  be  said  that  they  are  now  completed ;  but 
enough  has  been  done  to  permit  the  presentation  of  a  sys- 
tematic outline  of  this  subject.  Probably  no  subject  within 
the  whole  range  of  the  practice  of  the  engineer  has  de- 
manded or  has  received  more  attention  than  this;  and  prob- 
ably no  such  subject  has  been  less  satisfactorily  developed  in 


PREFACE.  V 

theory  and  less  thoroughly  investigated  experimentally  than 
iliis.  But  some  good  work  has  now  been  done,  and  well  done, 
during  late  years,  and  the  experience  of  the  steam-boiler 
insurance  and  inspection  companies  has  fortunately  served 
an  excellent  purpose  in  showing  that  the  element  of  mys- 
tery commonly  exists  only  in  the  imagination  of  writers  hav- 
ing more  poetry  than  logic  in  their  composition,  and  that 
the  causes  of  accident  are  wholly  preventible  and  controll- 
able. 

The  importance  of  this  matter  can  hardly  be  overesti- 
mated,, When,  as  estimated  by  the  late  Mr.  G.  H.  Babcock, 
there  were,  in  the  United  States,  in  1893,  10,000,000  horse- 
power, distributed  among  100,000  steam-boilers,  and  when, 
as  reported  by  the  insurance  companies,  there  were  dis- 
covered over  1,000  new  and  dangerous  defects  every  month 
by  the  company  and  risks  paid  on  20  explosions,  it  may 
well  be  imagined  that  this  subject  is  rated  by  the  engineer 
the  most  important  with  which  he  has  to  deal.  It  is,  how- 
ever, encouraging  to  note  that  the  probably  15,000  or  20,000 
dangerous  defects  annually  detected — by  explosion  or  in- 
spection— are  principally,  and  the  250  to  300  explosions 
per  annum,  in  the  United  States  alone,  substantially  all  of 
shell  boilers,  and  that  the  "sectional"  or  "safety"  boilers 
are  rapidly  becoming  substituted  for  the  older  types,  with 
resulting  diminution  of  danger. 

The  52  boilers,  of  25.000  collective  rated  horse-power 
exhibited  at  the  Exposition  at  Chicago,  in  1893,  were 
nearly  all  of  the  modern  type. 


CONTENTS. 


INTRODUCTION. 

ART.  PAGE. 

HEAT  ENERGY  OF  WATER  AND  STEAM                 •  3 

1.  THE  STORED  ENERGY  OF  THE  FLUID  3 

2.  FORMULAS  FOR  ENERGY  STORED      -  4 

3.  CALCULATED  QUANTITIES  OF  ENERGY  AND  TABLES  8 

4.  DEDUCTIONS  FROM  CALCULATIONS                 -        -  12 

5.  CURVES  OF  ENERGY  -  15 

STEAM  BOILER  EXPLOSIONS. 

6.  CHARACTER  OF  EXPLOSIONS  -  •  17 

7.  ENERGY  STORED  IN  STEAM  BOILERS  -  -  23 

8.  ENERGY  OF  STEAM  ALONE      -  -  32 

9.  EXPLOSION  DISTINGUISHED  FROM  BURSTING  -  34 

10.  CAUSES  OF  EXPLOSIONS  •  36 

11.  STATISTICS  OF  BOILER  EXPLOSIONS    -  -41 

12.  THEORIES  AND  METHODS       -  -    47 

13.  COLBURN  AND  CLARK*S  THEORY        -  -        49 

14.  CORROBORATORY  EVIDENCE  -         -        -        -        .52 

15.  ENERGY  IN  HEATED  METAL      -  61 

1 6.  STRENGTH  OF  HEATED  METAL      -         -        -        -    63 

17.  Low  WATER  AND  ITS  EFFECTS          ...          63 

1 8.  SEDIMENT  AND  INCRUSTATION       -         -         -        -73 

19.  ENERGY  IN  SUPER-HEATED  WATER  -         -        -        78 

20.  THE  SPHEROIDAL  STATE 86 


CONTENTS. 

21  STEADY  INCREASE  OF  PRESSURE  -                  94 

22  RELATIVE  SAFEEY  OF  BOILERS         -  -         -        -     98 
23.  DEFECTIVE  DESIGN  -         -       100 
24    DEFECTIVE  CONSTRUCTION   -  -                  -  105 

25.  DEVELOPED  WEAKNESS;  MULTIPLE  EXPLOSIONS    -   no 

26.  GENERAL  AND  LOCAL  DECAY     -  114 

27.  METHODS  OF  DECAY      ..--•-  117 

28.  TEMPERATURE  CHANGES  -  I22 

29.  MANAGEMENT               ...  -            125 

30.  EMERGENCIES    -         -         -         •  •        •        -128 

31.  RESULTS  OF  EXPLOSIONS       -  '31 

32.  EXPERIMENTAL  INVESTIGATIONS  -        -        -      256 

33.  CONCLUSIONS;    PREVENTIVES         *  °        -        -  *6£ 


INTRODUCTION.1 


HEAT-ENERGY  OF  STEAM  AND  WATER. 

I.  The  Stored  Energy  of  Steam  or  Water,  con- 
fined under  a  pressure  so  far  exceeding  atmospheric  as  to 
make  the  boiling  point  and  the  temperature  of  the  fluid 
considerably  greater  than  is  observed  where  water  be- 
comes vapor  in  the  open  air,  is  often  of  such  consider- 
able amount  as  to  make  its  determination  a  matter  of 
real  importance.  A  steam-boiler  explosion  is  but  the 
effect  of  causes  which  permit  the  transformation  of  a 
part  of  the  heat-energy  stored  in  the  vessel  into  mechan- 
ical energy,  and  the  application  of  that  energy  to  the 
production  of  results  which  are  often  terribly  impressive 
and  disastrous.  The  first  step,  therefore,  in  any  pro- 
posed scheme  of  study  of  this  important  and  attractive 
subject  is,  naturally,  an  examination  of  the  conditions 
under  which  energy  is  stored,  and  of  the  magnitude  of 
the  forces  and  energies  latent  in  steam  and  in  water 
when  confined  under  high  pressure.  The  first  attempt 
to  calculate  the  amount  of  energy  latent  in  steam,  and 
capable  of  greater  or  less  utilization  in  expansion  by 

*Mainly  from  a  paper  by  the  Author  "  On  Steam  Boilers  as  Maga- 
zines of  Explosive  Energy."  Trans.  Am.  Soc.  Mech.  Engrs.,  1884. 


4  IN  TR  OD  UC  TION. 

explosion,  was  made  by  Mr.  George  Biddle  Airy,*  the 
Astronomer  Royal  of  Great  Britain,  in  the  year  1863, 
and  by  the  late  Professor  Rankinet  at  about  the  same 
time. 

2.  Formulas  giving  the  energy  stored  in  steam  and 
in  water  are  now  well  established.  In  Rankine's  paper, 
just  referred  to,  for  example,  there  were  given  expres- 
sions for  the  calculation  of  the  energy  and  of  the  ulti- 
mate volumes  assumed  during  the  expansion  of  water 
into  steam,  as  follows,  in  British  and  in  Metric  meas- 
ures: 


TT-  77*  (T—212\  TT  _423.55   (T—  100)2. 

7H-H34-4'' 


36.76(^—212).  V  ^2.29(^—100) 

1  34.4  r+64s     • 


These  formulas  give  the  energy  in  foot-pounds  'and 
kilogrammeters,  and  the  volumes  in  cubic  feet  and  cubic 
meters.  They  may  be  used  for  temperatures  not  found 
in  the  tables  to  be  given,  but,  in  view  of  the  complete- 
ness of  the  latter,  it  will  probably  be  seldom  necessary 
for  the  engineer  to  resort  to  them. 

The  quantity  of  work  and  of  energy  which  may  be 
liberated  by  the  explosion,  or  utilized  by  the  expan- 
sion, of  a  mass  of  mingled  steam  and  water  has  been 
shown  by  Rankine  and  by  Clausius,  who  determined 
this  quantity  almost  simultaneously,  to  be  easily  ex- 

*"  Numerical  Expression  of  the  Destructive  Energy  in  the  Explosions 
of  Steam  Boilers,"  Phil.  Mag.,  Nov.  1863. 
f  "  On  the  Expansive  Energy  of  Heated  Water  ";  ibid. 


STORED   ENERGY  OF  STEAM.  5 

pressed   in   terms   of  the   two   temperatures   between 
which  the  expansion  takes  place. 

When  a  mass  of  steam,  originally  dry,  but  saturated, 
so  expands  from  an  initial  absolute  temperature,  7i,  to 
a  final  absolute  temperature,  TZ,  if  J  is  the  mechanical 
equivalent  of  the  unit  of  heat,  and  //"is  the  measure,  in 
the  same  units,  of  the  latent  heat  per  unit  of  weight  of 
steam,  the  total  quantity  of  energy  exerted  against  the 
piston  of  a  non-condensing  engine,  by  unity  of  weight 
of  the  expanding  mass  is,  as  a  maximum, 

-1-hyp.  log.+  T-H.  .  .  (A. 


This  equation  was  published  by  Rankine  a  genera- 
tion ago.*  _ 

When  a  mingled  mass  of  steam  and  water  similarly 
expands,  if  M  represents  the  weight  of  the  total  mass 
and  m  is  the  weight  of  the  steam  alone,  the  work  done 
by  such  expansion  will  be  measured  by  the  expression, 


-i-  hyp.  log.         +  m 


This  equation  was  published  by  Clausius  in  substan- 
tially this  form.t 

It  is  evident  that  the  latent  heat  of  the  quantity  m, 
which  is  represented  by  mH,  becomes  zero  when  the 
mass  consists  solely  of  water,  and  that  the  first  term  of 

*  Steam  Engine  and  Prime  Movers,  p.  387. 

\  Mechanical  Theory  of  Heat,  Browne's  Translation,  p.  283. 


6  INTRODUCTION. 

the  second  member  of  the  equation  measures  the 
amount  of  energy  of  heated  water  which  may  be  set 
free,  or  converted  into  mechanical  energy,  by  explosion. 
The  available  energy  of  heated  water,  when  explosion 
occurs,  is  thus  easily  measurable. 

As  has  already  been  stated,  this  method  was  first 
applied  by  Rankine  to  the  determination  of  the  avail- 
able energy  of  heated  water  for  several  selected  tem- 
peratures and  pressures.  It  had  long  been  the  intention 
of  the  Author  to  ascertain  the  magnitude  of  the  quanti- 
ties of  energy  residing,  in  available  form,  in  both  steam 
and  water,  for  the  whole  usual  range  of  temperatures 
and  pressures  familiar  to  the  engineer,  and  also  to  carry 
out  the  calculations  for  temperatures  and  pressures  not 
yet  attained,  except  experimentally,  but  which  are 
likely  to  be  reached  in  the  course  of  time,  as  the  con- 
stantly progressing  increase  now  observable  goes  on. 
The  maximum  attainable,  in  the  effort  to  increase  the 
efficiency  of  the  steam  engine  and  in  the  application  of 
steam  to  new  purposes,  cannot  be  to-day  predicted,  or 
even,  so  far  as  the  writer  can  see,  imagined.  High 
pressures  like  those  adopted  by  Perkins  and  by  Alban 
may  yet  be  found  useful.  It  was  therefore  proposed  to 
carry  out  the  tables  to  be  constructed  far  beyond  the 
limit  of  present  necessities. 

It  was  further  proposed  to  ascertain  the  weights  of 
steam  and  of  water  contained  in  each  of  the  more  com- 
mon forms  of  steam  boiler,  and  to  determine  the  total 
and  relative  amounts  of  energy  confined  in  each  under 
the  usual  conditions  of  working  in  every-day  practice, 


FORMULAS  FOR  ENERGY.  7 

and  thus  to  ascertain  their  relative  destructive  power  in 
case  of  explosion. 

At  the  commencement  of  this  work,  the  Author  em- 
ployed the  late  Mr.  W.  G.  Cartwright,  as  compu- 
ter, and,  with  his  aid,  prepared  tables  extending  from 
50  pounds  per  square  inch  to  100  at  intervals  of  ten 
pounds,  up  to  250  with  intervals  of  25  pounds,  then 
300,  and  up  to  1000  'pounds  per  square  inch  by 
100  pounds,  and  with  larger  intervals  up  to  10,000 
and  20,000  pounds.  The  available  energy  of  the 
heated  water  was  computed,  the  energy  obtain- 
able from  the  so-called  "  latent  heat,"  and  their 
sum,  i.  e.,  the  available  energy  of  steam  per  unit 
of  weight.  In  the  course  of  this  work,  each  figure 
was  calculated  independently  by  two  computers,  and 
thus  checked.  As  a  further  check,  the  figures  so  ob- 
tained were  plotted,  and  the  curve  representing  the  law 
of  their  variation  was  drawn.  This  was  a  smooth  curve  of 
moderate  curvature  and  an  incorrect  determination  was 
plainly  revealed,  and  easily  detected,  by  falling  outside 
the  curve.  Three  curves  were  thus  constructed,  which 
will  be  given  later:  (i)  The  Curve  of  Available  Energy 
of  Heated  Water ;  (2)  The  Curve  of  Available  Energy 
of  Latent  Heat ;  (3)  the  Curve  of  Available  Energy  of 
Steam.  The  second  of  these  curves  presents  an  inter- 
esting peculiarity  which  will  be  pointed  out  when 
studying  the  forms  of  the  several  curves  and  the  tables 
of  results. 

The  work  was  interrupted  by  more   pressing  duties, 
and  was  finally  resumed  in  the  spring  of  1884  and  com- 


8  INTRODUCTION. 

pleted  in  the  form  now  presented.  The  computers  of 
the  more  complete  tables  here  given  were  Messrs. 
Ernest  H.  Foster,  and  Kenneth  Torrance,  who, 
pursuing  the  same  method  as  was  originally  adopted 
for  the  earlier  computations,  have  revised  the  whole 
work,  recalculating  every  figure,  extending  the  tables 
by  interpolation,  and  carrying  them  up  to  a  still 
higher  pressure  than  was  originally  proposed.  The 
tables  here  presented  range  from  20  pounds  per  square 
inch,  (1.4  kgs.  per  sq.  cm.)  up  to  100,000  per  square 
inch  (7,030.83  kgs.  per  sq.  cm.)  the  maximum  probably 
falling  far  beyond  the  range  of  possible  application,  its 
temperature  exceeding  that  at  which  the  metals  retain 
their  tenacity,  and,  in  some  cases,  exceeding  their  melt- 
ing points.  These  high  figures  are  not  to  be  taken  as 
exact  The  relation  of  temperature  to  pressure  is  ob- 
tained by  the  use  of  Rankine's  equation,  of  v/hich  it  can 
only  be  said  that  it  is  wonderfully  exact  throughout  the 
range  of  pressures  within  which  experiment  has  ex- 
tended, and  within  which  it  can  be  verified.  The  val- 
ues estimated  and  tabulated  are  probably  quite  exact 
enough  for  the  present  purposes  of  even  the  military 
engineer  and  ordnance  officer.  The  form  of  the  equa- 
tion, and  of  the  curve  representing  the  law  of  variation 
of  pressure  with  temperature,  indicates  that,  if  exact  at 
the  familiar  pressures  and  temperatures,  it  is  not  likely 
to  be  inexact  at  higher  pressures.  The  curve,  at  its 
upper  extremity  becomes  nearly  rectilinear. 

3.    The  Calculated  Energy  of  Water  and  Steam 
are  given  in  the  table  which  follows,  and  which  presents 


CALCULA  TED  ENERG  Y.  9 

the  values  of  the  pressures  in  pounds  per  square  inch 
above  a  vacuum,  the  corresponding  reading  of  the  steam- 
gauge  (allowing  a  barometric  pressure  of  14.7  pounds 
per  square  inch),  and  the  same  pressures  reckoned  in 
atmospheres,  the  corresponding  temperatures  as  given  by 
the  Centigrade  and  the  Fahrenheit  thermometers,  and 
as  reckoned  both  from  the  usual  and  the  absolute  zeros. 
The  amount  of  the  explosive  energy  of  a  unit  weight  of 
water,  of  the  latent  heat  in  a  unit  weight  of  steam,  and 
the  total  available  heat- energy  of  the  steam,  are  given 
for  each  of  the  stated  temperatures  and  pressures 
throughout  the  whole  range  in  British  measures,  atmo- 
spheric pressures  being  assumed  to  limit  expansion. 
The  values  of  the  latent  heats  are  taken  from  Regnault, 
for  moderate  pressures,  and  are  calculated  for  the 
higher  pressures,  beyond  the  range  of  experiment,  by 
the  use  of  Rankine's  modification  of  Regnault's  formula. 


10 


IN  TROD  UCTION. 


w 

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sfa&&s 


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till 

Pill  Si 

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t^  ON  O^oo 


tON    N    M    N 


M  ^-roi^^r^ro  t^»oo  o^ 
o  m  oi  00  roco  0)  'O  O  •*•  t~>  Q  fT- 
^-  u~/o  vo  t^  t>.oo  OO&.O-.  ONOO 


vo  oo  o_<  ov  t^  HI  oo  f^vq  10  t>.vo  t~-  i 
N°  vd  H  -4-  M  oo  rood  -i-  6  t>.  rood  ' 
^  °o  oo  Jo  o*  H?  ! 
It^oo  c£o?  ! 


I  l>>  P)  vo    ro  Ov  t^  -4-  OWO 


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fOM  c»  ^-M  irjo^*^-  o>^o  H  o  fo  10 

-^-oo  w  vo   M   ir>  0s  -"t-oo   rooo   w  vo   O 

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^  H  VO    6    ^OO    H    •^•(--^d    NlOt^O    N    -4-VO*  GO    ON  H    CO  ir> 
11   M   w   rof>m-*-T*--*-miO»r)  lovo  vovovovovo   r-»t^t^ 


moo  o  O  oo  ir>  M  1000  ov  o  O 


s  IP 


OO     M      ^VO     fx   U*>   M 

_  10  a*  rooo  ^-  M  o 

•^-  1OOC3    CJVO    M\O    WOO    ^O    t*N.^-Mo6    IOW    O    t>.  »O  CO  O 

51  ^  s?  s  Sv  Sv  Sv  Sv  Sv  &  a^^^s  gg  §§  g§  cS-cg-^.s- 


10  O  >o  O  »n  O  »A  6  10  O  10  O  10  O  in  O  in  O  in  O  >o  O  « 
M  HI  c*  o»  rom^-^u^  invo  vo  t^.  t^.oo  oo  Ov  Ov  O  O  HI  M 


inOin 

OMM 


AVAILABLE  ENERGY. 


II 


oi  4-  4-  m  in  tx  M  NO'  me  -4-  in  N"  o"  4-No"  -4-  4-  d  oo  moo"  «'  O  o"  o*  tx  -4-  «  4- 

m  m  m  0  O  tx  in  »*  tx  moo  «  tx  M  oo  ^  moo  oo  ONOO  ONNO  txoo  O  w  CNI  M  « 
m  in  tx  ON  M  CNI  ^-NO  tx  ON  o  w  m  in  tx  M  mintxintxONONmmM  tx  N  rx  ON 

ix  m  o  ^  ON  mNO  ON  W  ^-NO  ix  o*  ON  o  O  **  0  moo  w  N  m  CN)  mN^  m  m  ON  m 
m  m  ixoo  ON  «  CNI  m  mNO  txoo  ON  o  mNO  tx  o  O  m  ON  •*  m  ON 

N~  ONNO  moo"  •*  N  5-c§  CNI  oo  NO"  ?  in  mN?  oo  dN«"S?.txiiCONO^">? 

d  CNI  m  «nNO  oo"  ON  d  CN!  m  4-  in  txoo  d  oi  in  tx  ONNO  d  m  ON  ON  inNO  in  4-  M  inoo' 

in  in  in  in  in  in  inNC  NONONONONONO    lxJxtxlxtxN.N6    «    ^ixQ    C1    ^NO  OO    ON  in 

•*'*'*"*'*''*-«-'*'*-^-'*^--<«--*-'*^-'*'-<f--<-in  mNO  NONO  txtxrxtxrxtx'* 

M"  mNo"  ON  M  -*-NO"  ON  M  4-No"  oo"  d  N"  NO"  M  \r>  ON  «  oo"  oo"  4-  c>  m  d>  tx  CN)  in 
M  M  M  M  N  CNI  CNI  CN)  mmmm^^-^inin  mNO  ONO  ONO  C*NO  O  -^tx 
oooooooooooooooooooooooooooooooooooooooo  o  i-  »  CN)  CN)  mmm 

°/tT'u?"  ^T"^  *>".  "O00.  °.  N.  T  *?*°.  °°.  °!  °^  °,  *  °°.  *>  ^  lxo°.  ?  N.  *?  1  * 
?  Sf>  Jn^S>N2  NO^NO"*'  S.  S  ^*  ^**-1*  -**-*^*  *>  *  ^>v°'  f^°9  <T>  t>  >n  w*  4-  «o  « 

m  M  ON  mNO  O  ^  CN)  o  oo  NO  ^-co  NO^-^t-MONOwo  ooo  ^ONminmtxM  o 
C*NO  txM  rx-^-in-^-tx  ONOO  •^•mwNONO  ONM  mONin-^-mixm  txoo  m  •*•  o  ^i- 

O)  NO  NO  CN)  M  txNO  ONNO  -O  0  OO  ON  m  O-OO  NO  -4-NO  S  m  O  O  tx  m  ?  ON  S  m  ?  O 

NO  in  inNO  txoo  o  CN)  moo  CNI  in  ON  -^  m  in  ONNO  moo  ^-  ONOO  NO  txoo  ON  ^-NO  w  m 
NO"  4'indoooo"  inmM  o^oo" NO"  4-mdoo  m«  d  d  d  md  4-in*-*  ONC>CN)  inin 
NONONO'O  ininmiHin^--"*--"*-'*-*-  *•  m  m  m  moo  cs  •<•  ON  4^  o  tx  m  O  oo  in  o 
oo  oo  oo  oo  oo  ONOO  oo  oo  oo  oo  oo  oo  oo  oo  oo  oo  oo  oo  tx  P.NO  in  in  in  ?  ¥  *-m  m  m 

dN^^dd'^^^100''' 

rOfO(^cnf^rtc^fO(^*Aroro<^rOfO(^fOf^f^c^f<)ror^ 

O  in  d  "^6  «n  O  »o  O  »o  O  «n  O  inuS^ioioiriioioinioinioioioinioioio 

w  N  m  ro  ^  ^-  m  »n\o  NO  tx  t^oo  oo  o  O  M  w  moo  oooooooooooooooooooooo 

MMMiHMMMMMMMMMMMeiC«C4CI'^*O«O>'C>C>O^C^p^P^P^Q^C^ 

loO^O^O^no^O    "^O^^OOO 


j  2  IN  TROD  UC  TION. 

4.  The  Deductions  from  these  calculations  are  of 
extraordinary  importance  and  interest.  Studying  the 
table,  the  most  remarkable  fact  noted  at  the  lower  press- 
ures is  the  enormous  difference  in  the  amounts  of  en- 
ergy, in  available  form,  contained  in  the  water  and  in 
the  steam,  and  between  the  energy  of  sensible  heat  and 
that  of  latent  heat,  the  sum  of  which  constitutes  the 
total  energy  of  the  steam.  At  20  pounds  per  square 
inch  above  zero  (1.36  atmos.),  the  water  contains  but 
145.9  foot-pounds  per  pound  ;  while  the  latent  heat  is 
equivalent  to  16,872.9  foot-pounds,  cr  more  than  115 
times  as  much ;  i.  e.,  the  steam  yields  1 1 5  times  as 
much  energy  in  the  form  of  latent  heat,  per  pound,  as 
does  the  water  from  which  it  is  formed,  at  the  same  tem- 
perature. The  temperature  is  low  ;  but  the  amount  of 
energy  expended  in  the  production  of  the  molecular 
change  resulting  in  the  conversion  of  the  water  into 
steam  is  very  great,  in  consequence  of  the  enormous  ex- 
pansion then  taking  place.  At  50  pounds,  the  ratio  is 
20  to  I  ;  at  IOO  pounds  per  square  inch,  it  is  14  to  I, 
at  500  it  is  5  to  I  ;  while  at  5000  pounds  the  energy  of 
latent  heat  is  but  1.4  that  of  the  sensible  heat.  The 
two  quantities  become  equal  at  75°°  pounds.  At  the 
highest  temperature  and  pressure  tabled,  the  same  law 
would  make  the  latent  heat  negative;  it  is  of  course  un- 
certain what  is  the  fact  at  that  point. 

At  50  pounds  per  square  inch  the  energy  of  heated 
water  is  2550.4  foot-pounds,  while  that  of  the  steam  is 
68,184,  or  enough  to  raise  its  own  weight  to  a  height  in 
each  case  of  a  half-mile  or  of  12  miles.  At  75  pounds 


STEAM  AND  ITS  PROPERTIES. 


FIG.  «. — CURVE  OF  HEAT  IN  STKAM 


THE   STEAM-BOILER. 


25000 


1009        £0tt         8000         4000          6000          6000          7000          8U»          9000          WOOD        U669 
ABSOLUTE  PRESSURE  IN  FOOT  POUNDS  PER.  SQ.  IN. 

F  c.  2. — CURVE  OF  HEAT-ENERGY  IN  STEAM. 


THE   CURVE   OF  ENERGY.  15 

the  figures  are  4816  and  90,739,  or  equivalent  to  the 
work  demanded  to  raise  the  unit  weight  to  a  height  of 
four-fifths,  and  of  about  17  miles,  respectively.  At  100 
pounds  the  heights  are  over  one  mile  for  the  water,  and 
above  20  miles  for  the  steam.  The  latent  heat  is  not, 
however,  all  effective. 

5.  The  Curve  of  Energy  obtained  by  plotting  the 
tabulated  figures  and  determining  the  form  of  the  curve 
representing  the  law  of  variation  of  each  set,  are  seen  in 
the  peculiar  set  of  diagrams  exhibited  in  the  accom- 
panying engravings.  In  Figure  I  are  seen  the  curves  of 
absolute  temperature  and  of  latent  heat  as  varying  with 
variation  of  pressure.  They  are  smooth  and  beauti- 
fully formed  lines,  but  have  no  relation  to  any  of  the 
familiar  curves  of  the  text  books  on  co-ordinate  geome- 
try. In  Figure  2  are  given  the  curves  of  available  en- 
ergy of  the  water  of  latent  heat,  and  of  steam.  The 
first  and  third  have  evident  kinship  with  the  two  curves 
given  in  the  preceding  illustration;  but  the  curve  of 
energy  of  latent  heat  is  of  an  entirely  different  kind, 
and  is  not  only  peculiar  in  its  variation  in  radius  of 
curvature,  but  also  in  the  fact  of  presenting  a  maximum 
ordinate  at  an  early  point  in  its  course.  This  maximum 
is  found  at  a  pressure  of  about  one  ton  per  square  inch, 
a  pressure  easily  attainable  by  the  engineer. 

Examining  the  equations  of  those  curves  it  is  seen 
that  they  have  no  relation  to  the  conic  sections,  and 
that  the  curve,  the  peculiarities  of  which  are  here  noted, 
is  symmetrical  about  one  of  its  abscissas,  and  that  it 
must  have,  if  the  expression  tolds  for  such  pressures, 


1 6  INTRODUCTION. 

another  point  of  contrary  flexure  at  some  enormously 
high  pressure  and  temperature.  The  formula  is  not, 
however,  a  "  rational  "  one,  and  it  is  by  no  means  cer- 
tain that  the  curve  is  of  the  character  indicated;  al- 
though it  is  exceedingly  probable  that  it  may  be.  The 
presence  of  the  characteristic  point,  should  experiment 
finally  confirm  the  deduction  here  made,  will  be  likely 
to  prove  interesting,  and  it  may  be  important ;  its  dis- 
covery may  possibly  prove  to  be  useful. 

The  curve  of  energy  of  steam  is  simply  the  curve  ob- 
tained by  the  superposition  of  one  of  the  preceding 
curves  upon  the  other.  It  rises  rapidly  at  first,  with 
increase  of  temperature,  then  gradually  rises  more 
slowly,  turning  gracefully  to  the  right,  and  finally  be- 
coming nearly  rectilinear.  The  curve  of  available 
energy  of  heated  water  exhibits  similar  characteristics  ; 
but  its  curvature  is  more  gradual  and  more  uniform.  It 
must  be  observed,  however,  that  the  expression  is  here 
employed  for  pressures  far  outside  the  limits  of  either 
common  experience  or  direct  experiment  and  hence 
cannot  be  checked.  It  may  depart,  in  an  important 
degree,  at  its  higher  ranges  from  the  actual  fact. 


STEAM  BOILER  EXPLOSIONS. 


6.  Steam  Boiler  Explosions  are  among  the  most 
terrible  and  disastrous  of  the  many  kinds  of  accidents 
the  introduction  of  which  has  marked  the  advancement 
of  civilization  and  its  material  progress.*  Introduced 
by  Captain  Savery  at  the  beginning  of  the  i8th  Cen- 
tury, with  the  first  attempts  to  apply  steam-power  to  use- 
ful purposes,  they  have  increased  in  frequency  and  in 
their  destructiveness  of  liie  and  property  continually, 
with  increasing  steam -pressures,  and  the  uninterrupted 
growth  of  these  magazines  of  stored  energy,  until, 
to-day,  the  amount  of  available  energy  so  held  in  control, 
and  liable  at  times  to  break  loose,  is  often  as  much  as 
two,  or  even  three,  millions  of  foot-pounds  (276,500  to 
414,760  kilogram-meters),  and  sufficient  to  raise  the 
enclosing  vessel  10,000,  or  even  20,000  feet  (3048  to 
6096  m.)  into  the  air,  the  fluid  having  a  total  energy, 
pound  for  pound,  only  comparable  with  that  of  gun- 
powder. 

*Portions  of  this  chapter  are  taken  from  the  notes  from  which  a  paper 
by  the  Author  "  On  Steam  Boilers  as  Magazines  of  Explosive  Energy  " 
was  prepared.  See  Trans.  Am.  Society  M.  E.,  1884  ;  and  Jour.  Frank. 
Inst.,  Nov.,  1884.  Manual  of  Steam-boilers,  Thurston  ;  Chap.  XV. 


1 8  STEAM  BOILER  EXPLOSIONS. 

A  committee  of  the  British  Association,  at  the  session 
of  1869,  reporting  on  this  subject,  after  remarking  that 
explosions  were  occurring  still,  with  their  accustomed 
frequency  and  fatality,  go  on  to  say  :* 

"  Sad  as  it  is  when  those  connected  with  boilers  and 
who  gain  their  livelihood  from  working  them  are  injured, 
it  is  even  more  so  when  outsiders  who  have  no  interest 
in  their  use,  or  control  over  their  management,  are 
victimized  by  their  explosion,  more  especially  when 
those  victims  are  women  and  children.  Such,  however, 
is  by  no  means  an  infrequent  occurrence.  In  one  case, 
a  child,  asleep  in  its  bed,  unconscious  of  all  danger,  was 
killed  on  the  spot  by  a  fragment  of  an  exploded  boiler 
sent  through  the  roof  like  a  thunderbolt.  In  a  second 
case  a  young  woman  working  at  her  needle  in  an  upstairs 
room,  in  her  own  dwelling,  was  struck  by  a  boiler  which 
was  hurled  from  its  seat  and  dashed  against  the  window 
at  which  she  sat.  The  injury  was  serious — her  leg  had 
to  be  amputated,  and  death  shortly  after  ensued.  In  a 
third  case,  just  as  an  infant  was  making  its  first  essay 
across  the  kitchen-floor  in  a  collier's  cottage,  a  fragment 
from  an  exploded  boiler  came  crashing  through  the  roof, 
and  striking  down  the  child,  killed  it  on  the  spot.  In  a 
fourth  case,  a  woman  was  standing  at  her  own  cottage 
door  with  an  infant  in  her  arms,  when  one  of  the  bricks 
sent  flying  through  the  air  by  the  bursting  of  a  boiler 
struck  the  little  one  on  the  head,  and  killed  it  in  its 
mother's  arms.  In  a  fifth  case,  a  group  of  boys  were 

*London  Engineer,  Oct.  8,  1869,  p.  237. 


STEAM  BOILER  EXPLOSIONS.  19 

sporting  in  a  meadow,  when  the  boiler  of  a  locomotive 
engine,  just  drawn  up  at  an  adjoining  station,  burst,  and 
scattering  its  fragments  among  the  group,  killed  one  of 
the  boys  on  the  spot  and  injured  another."  And  many 
more  such  incidents  might  be  related. 

In  this  and  the  following  article  it  is  proposed  to 
present  the  results  of  a  series  of  calculations  relating  to 
the  magnitude  of  the  available  energy  contained  in 
masses  of  steam  and  of  water  in  steam-boilers.  This 
energy  has  been  seen  to  be  measured  by  the  amount  of 
work  which  may  be  obtained  by  the  gradual  reduction 
of  the  temperature  of  the  mass  to  that  due  atmospheric 
pressure  by  continuous  expansion. 

The  subject  is  one  which  has  often  attracted  the  atten- 
tion of  both  the  man  of  science  and  the  engineer.  Its 
importance,  both  from  the  standpoint  of  pure  science 
and  from  that  of  science  applied  in  engineering  and  the 
minor  arts,  is  such  as  would  justify  the  expenditure  of 
vastly  more  time  and  attention  than  has  ever  yet  been 
given  it  Mr.  Airy*  and  Professor  Rankinet  published 
papers  on  this  subject  in  the  same  number  of  the  Phil- 
osophical Magazine  (Nov.,  1863),  the  one  dated  the  3d 
of  September  and  the  other  the  5th  of  October  of  that 
year.  The  former  had  already  presented  an  abstract  of 
his  work  at  the  meeting  of  the  British  Association  of 
that  year. 

In  the  first  of  these  papers,  it  is  remarked  that  "  very 

*Numerical  Expression  of  the  Destructive  Energy  in  the  Explosions 
of  Steam  Boilers. 

f"  On  the  Expansive  Energy  of  Heated  Water. 


20  STEAM  BOILER  EXPLOSIONS. 

little  of  the  destructive  effect  of  an  explosion  is  due  to 
the  steam  which  is  confined  in  the  steam-chamber  at 
the  moment  of  the  explosion.  The  rupture  of  the 
boiler  is  due  the  expansive  power  common  at  the 
moment  to  the  steam  and  the  water,  both  at  a  tempera- 
ture higher  than  the  boiling  point ;  but  as  soon  as  the 
steam  escapes,  and  thereby  diminishes  the  compressive 
force  upon  the  water,  a  new  issue  of  steam  takes  place 
from  the  water,  reducing  its  temperature;  when  this 
escapes,  and  further  diminishes  the  compressive  force, 
another  issue  of  steam  of  lower  elastic  force  from  the 
water  takes  place,  again  reducing  its  temperature  ;  and 
so  on,  till  at  length  the  temperature  of  the  water  is 
reduced  to  the  atmospheric  boiling  point,  and  the  press- 
ure of  the  steam  (or  rather  the  excess  of  steam-pressure 
over  atmospheric  pressure)  is  reduced  to  o." 

Thus  it  is  shown  that  it  is  the  enormous  quantity  of 
steam  so  produced  from  the  water,  during  this  continu- 
ous but  exceedingly  rapid  operation,  that  produces  the 
destructive  effect  of  steam-boiler  explosions.  The  action 
of  the  steam  which  may  happen  to  be  present  in  the 
steam- space  at  the  instant  of  rupture  is  considered 
unimportant. 

Mr.  Airy  had,  as  early  as  1 849,  endeavored  to  deter- 
mine the  magnitude  of  the  effect  thus  capable  of  being 
produced,  but  had  been  unable  to  do  so  in  consequence 
of  deficiency  of  data.  His  determinations,  as  pub- 
lished finally,  were  made  at  his  request  by  Professor  W. 
H.  Miller.  The  data  used  are  the  results  of  the  experi- 
ments of  Regnault  and  of  Fairbairn  and  Tate,  on  the 


ENERGY  OF  BOILER  EXPLOSIONS.  2J 

relations  of  pressure,  volume  and  temperature  of  steam, 
and  of  an  experiment  by  Mr.  George  Biddle,  by  which 
it  was  found  that  a  locomotive  boiler,  at  four  atmos- 
pheres pressure,  discharged  one-eighth  of  its  liquid 
contents  by  the  process  of  continuous  evaporization 
above  outlined,  when,  the  fire  being  removed,  the  press- 
ure was  reduced  to  that  of  the  atmosphere.  The 
process  of  calculation  assumes  the  steam  so  formed  to 
be  applied  to  do  work  expanding  down  to  the  boiling 
point,  in  the  operation.  The  work  so  done  is  compared 
with  that  of  exploding  gunpowder,  and  the  conclusion 
finally  reached  is  that  "  the  destructive  energy  of  one 
cubic  foot  of  water,  at  a  temperature  which  produces 
the  pressure  of  60  Ibs.  to  the  square  inch,  is  equal  to 
that  of  one  pound  of  gunpowder." 

The  work  of  Rankine  is  more  exact  and  more  com- 
plete, as  well  as  of  greater  practical  utility.  The 
method  adopted  is  that  which  has  been  described,  and 
involves  the  application  of  the  formulas  for  the  trans- 
formation of  heat  into  work  which  had  been  ten  years 
earlier  derived  by  Rankine  and  by  Clausius,  indepen- 
dently. This  paper  would  seem  to  have  been  brought 
out  by  the  suggestion  made  by  Airy  at  the  meeting  of 
the  British  Association.  Rankine  shows  that  the  energy 
developed  during  this,  which  is  an  adiabatic  method  of 
expansion,  depends  solely  upon  the  specific  heat  and 
the  temperatures  at  the  beginning  and  the  end  of  the 
expansion,  and  has  no  dependence,  in  any  manner,  upon 
any  other  physical  properties  of  the  liquid.  He  then 
shows  how  the  quantity  of  energy  latent  in  heated 


22  STEAM  BOILER  EXPLOSIONS 

water  may  be  calculated,  and  gives,  in  illustration,  the 
amount  so  determined  for  eight  temperatures  exceeding 
the  boiling  point.  This  subject  attracted  the  attention 
of  engineers  at  a  very  early  date.  Familiarity  with 
the  destructive  effects  of  steam-boiler  explosions,  the 
singular  mystery  that  has  been  supposed  to  surround 
their  causes,  the  frequent  calls  made  upon  them,  in  the 
course  of  professional  practice  and  of  their  studies,  to 
examine  the  subject  and  to  give  advice  in  matters  relat- 
ing to  the  use  of  steam,  and  many  other  hardly  less 
controlling  circumstances,  invest  this  matter  with  an 
extraordinary  interest. 

A  steam-boiler  is  a  vessel  in  which  is  confined  a  mass 
of  water,  and  of  steam,  at  a  high  temperature,  and  at  a 
pressure  greatly  in  excess  of  that  of  the  surrounding 
atmosphere.  The  sudden  expansion  of  this  mass  from 
its  initial  pressure  down  to  that  of  the  external  air, 
occurring  against  the  resistance  of  its  "  shell  "  or  other 
masses  of  matter,  may  develop  a  very  great  amount  of 
work  by  the  transformation  of  its  heat  into  mechanical 
energy,  and  may  cause,  as  daily  occurring  accidents 
remind  us,  an  enormous  destruction  of  life  and  property. 
The  enclosed  fluid  consists,  in  most  cases,  of  a  small 
weight  of  steam  and  a  great  weight  of  water.  In  a 
boiler  of  a  once  common  and  still  not  uncommon 
marine  type,  the  Author  found  the  weight  of  steam  to  be 
less  than  250  pounds,  while  the  weight  of  water  was 
nearly  40,000  pounds.  As  will  be  seen  later,  under 
-uch  conditions,  the  quantity  of  energy  stored  in  the 
water  is  vastly  in  excess  of  that  contained  in  the  steam, 


STORED  ENERGY*  2$ 

notwithstanding  the  fact  that  the  amount  of  energy  per 
unit  of  weight  of  fluid  is  enormously  the  greater  in  the 
steam.  A  pound  of  steam,  at  a  pressure  of  six  atmos- 
pheres (88.2  pounds  per  square  inch),  above  zero  of 
pressure,  and  at  its  normal  temperature,  I77C.  (3I9°F.), 
has  stored  in  it  about  75  British  Thermal  Units  (32 
Calories),  or  nearly  70,000  foot-pounds  of  mechanical 
energy  per  unit  of  weight,  in  excess  of  that  which  it 
contains  after  expansion  to  atmospheric  pressure.  A 
pound  of  water  accompanying  that  steam,  and  at  the 
same  pressure,  has  stored  within  it  about  one-tenth  as 
much  available  energy.  Nevertheless,  the  disproportion 
of  weight  of  two  fluids  is  so  much  greater  as  to  make 
the  quantity  of  energy  stored  in  the  steam  contained  in 
the  boiler  quite  insignificant  in  comparison  with  that 
contained  in  the  water.  These  facts  are  fully  illustrated 
by  the  figures  presented. 

7.  The  Energy  Stored  in  steam  boilers  is  capable  of 
very  exact  computation  by  the  methods  already  de- 
scribed, and  the  application  of  the  results  there  reached 
gives  figures  that  are  quite  sufficient  to  account  for  the 
most  violently  destructive  of  all  recorded  cases  of  ex- 
plosion. 

A  steam-boiler  is  not  only  an  apparatus  by  means  of 
which  the  potential  energy  of  chemical  aflinity  is  ren- 
dered actual  and  available,  but  it  is  also  a  storage- 
reservoir,  or  a  magazine,  in  which  a  quantity  of  such 
energy  is  temporarily  held,  and  this  quantity,  always 
enormous,  is  directly  proportional  to  the  weight  of 
water  and  of  steam  which  the  boiler  at  the  time 
contains. 


24  STEAM  BOILER  EXPLOSIONS. 

Comparing  the  energy  of  water  and  of  steam  in  the 
steam-boiler  with  that  of  gunpowder,as  used  in  ord- 
nance, it  has  been  found  that  at  high  pressures  the 
former  become  possible  rivals  of  the  latter.  The  energy 
of  gunpowder  is  somewhat  variable,  but  it  has  been 
seen  that  a  cubic  foot  of  heated  water,  under  a  pressure 
of  60  or  70  pounds  per  square  inch,  has  about  the  same 
energy  as  one  pound  of  gunpowder.  The  gunpowder 
exploded  has  energy  sufficient  to  raise  its  own  weight 
to  a  height  of  nearly  50  miles ;  while  the  water  has 
enough  to  raise  that  weight  about  one-sixtieth  that 
height.  At  a  low  red  heat,  water  has  about  40  times 
this  latter  amount  of  energy  in  a  form  to  be  so  ex- 
pended. Steam,  at  4  atmospheres  pressure,  yields 
about  one-third  the  energy  of  an  equal  weight  of  gun- 
powder. At  7  atmospheres,  it  gives  as  much  energy  as 
two-fifths  of  its  own  weight  of  powder,  and  at  higher 
pressures  its  available  energy  increases  very  slowly. 

Below  are  presented  the  weights  of  steam  and  of 
water  contained  in  each  of  the  more  common  forms  of 
steam-boilers,  the  total  and  relative  amounts  of  energy 
confined  in  each  under  the  usual  conditions  of  working 
in  every-day  practice,  and  their  relative  destructive 
power  in  case  of  explosion. 

In  illustration  of  the  results  of  application  of  Ine 
computations  which  have  been  given,  and  for  the 
purpose  of  obtaining  some  idea  of  the  amount  of 
destructive  energy  stored  in  steam  boilers  of  familiar 
forms,  such  as  the  engineer  is  constantly  called  upon  to 
deal  with,  and  such  as  the  public  are  coiuinually  en- 


STORED  ENERGY,  25 

dangered  by,  the  following  table  has  been  calculated. 
This  table  is  made  up  by  Mr.  C.  A.  Carr,  U.  S.  N.,  from 
notes  of  dimensions  of  boilers  designed  by,  or  managed, 
at  various  times,  by  the  Author,  or  in  other  ways  having 
special  interest  to  him.  They  include  nearly  all  of  the 
forms  in  common  use,  and  are  representative  of  familiar 
and  ordinary  practice. 

No.  I  is  the  common,  simple,  plain  cylindrical  boiler. 
It  is  often  adopted  when  the  cheapness  of  fuel  or  the 
impurity  of  the  water-supply  renders  it  unadvisable  to 
use  the  more  complex,  though  more  efficient,  kinds.  It 
is  the  cheapest  and  simplest  in  form  of  all  the  boilers. 
The  boiler  here  taken  was  designed  by  the  Author  many 
years  ago  for  a  mill  so  situated  as  to  make  this  the  best 
form  for  adoption,  and  for  the  reasons  above  given.  It 
is  thirty  inches  in  diameter,  thirty  feet  long,  and  is  rated 
at  ten  H.  P.,  although  such  a  boiler  is  often  forced  up 
to  double  that  capacity.  The  boiler  weighs  a  little  over 
a  ton,  and  contains  more  than  twice  its  weight  of  water. 
The  water,  at  a  temperature  corresponding  to  that  of 
steam  at  100  pounds  pressure  per  square  inch,  contains 
over  46,600,000  foot-pounds  of  available  explosive  en- 
ergy, while  the  steam,  which  has  but  one-fifth  of  one 
per  cent,  of  the  weight  of  the  water,  stores  about 
700,000  foot-pounds,  giving  a  total  of  47,000,000  foot- 
pounds, nearly,  or  sufficient  to  raise  one  pound  nearly 
10,000  miles.  This  is  sufficient  to  throw  the  boiler 
19,000  feet  high,  or  nearly  four  miles,  and  with  an  ini- 
tial velocity  of  projection  of  1,100  feet  per  second. 

Comparing  this  with  the  succeeding  cases,  it  is  seen 


2 6  STEAM  BOILER  EXPLOSIONS. 

TOTAL    STORED*    ENERGY   OF  STEAM    BOILERS. 


Type. 

Are 

a  of 

Pressure. 
Lbs.  per 

Rated 
Power 

> 

Veight  o 

f 

G.  S. 

H.  S. 

Sq.  inch. 

H.  P. 

Boiler. 

Water. 

Steam. 

Sq.  1 

?eet. 

I  bs 

i  Plain  Cylinder  

15 

1  2O 

loo 

10 

2500 

5764 

11.325 

36 

3° 

60 

16950 

27471 

31  .45 

3  Two-Hue  Cylinder  
4  Plain  Tubular  
5  Locomotive  

20 

3° 

22 
3° 

400 

85L97 
1070 
1350 

150 
75 
125 
I25 

u 
III 

6775 
9500 
19400 
25000 

6840 
8255 
5260 
6920 

37.04 
20.84 
21.67 
31.19 

1            "            

20 
IJ 

12OO 
875 

125 
125 

600 

425 

20565 
14020 

6450 
6330 

25-65 
19.02 

9  Scotch  Marine  

32 

768 

75 

300 

27045 

11765 

29.8 

10                     "                      

ii  Flue  &  Return  Tubular 

12                               " 

13  Water  Tube  
14                         
15                         

50.5 
72.5 
72 
70 
IOO 
100 

III9.5 
2324 
1755 
2806 
3OOO 
3000 

75 
3° 
3° 

IOO 
IOO 
IOO 

350 

2OO 
1  80 
250 
250 
250 

37972 
56000 
56000 
34450 
45000 
54000 

i773<> 
42845 
48570 
21325 
28115 
13410 

47.2 
69.81 
73.07 
35.31 
58.5 
21.64 

TOTAL  STORED  ENERGY  OF  STEAM  BOILERS.— Continued. 


Type. 

Stored  Energy  in  (available) 

Energy 
per  Ib.  of 

Max. 
Height  of 
Project'n. 

Initial 
Velocity 

Water. 

Steam. 

Total. 

B'l'r 

Tot 
W't 

B'l'r 

Tot 

B'l'r 

Tot. 

Feet  per 

,  Foot  Ibs.—  —  \ 

r-Ft.lbs^ 

,—  Feet.-^ 

Second. 

i  Plain  Cylinder... 

46,605,200 

676,698 

47,281,898 

18913 

57M 

18913 

5714 

1103 

606 

2  Cornish  

57,570,750 

709,310 

58,260,060 

343  1 

1314 

3431 

I3I4 

471 

290 

3  Two-flue  Cyl'der 
4  Plain  Tubular.   . 

80,572,050 
50,008,790 

2,377,357 
1,022,731 

82.949,407 
51,031,521 

12243 
5372 

6076 
2871 

12243 

5372 

6076 
2871 

888 
588 

625 
430 

5  Locomotive  
7            "            

52,561,075 
69,148,790 
64,452,270 

1,483,896 
2,136,802 
1,766,447 

54,044,97! 
71,284,592 
66,218,717 

2786 
2851 
3219 

2189 
2231 
2448 

2786 
2851 
3219 

2180 
2231 
2448 

423 
428 
455 

375 
379 
397 

8             "            
9  Scotch  Marine  .  .  . 

64,253,160 
71,272,370 

1,302,431 
1,462,430 

65.555.591 
72,734,800 

4677 
2689 

3213 
1873 

4677 
2689 

3213 
1873 

549 
416 

455 
348 

10 
ii  Flue  &  Ret'n  Tblr 

107,408,340 
90,531,490 

2,316,392 
1,570,517 

109,724,732 
92,101,987 

2889 
1644 

1968 

2889 
1644 

1968 
93  x 

431 
325 

356 
245 

12                                  " 

102,628,410 

I,643,8S4 

104,272,264 

1862 

996 

1862 

996 

346 

253 

13  Water  Tube  

172,455,270 

2,108,110 

174,563,380 

5067 

3073 

5067 

3073 

445 

14                         

227,366,300 

3,513,830 

230,879,830 

5*3° 

3*55 

513° 

3*55 

575  !45° 

15                         

108,346,670 

109,624,283 

2030 

1626 

2030 

1626 

361 

323 

*  This  "  stored  "  energy  is  less  than  that  available  in  the  non-condensing  engine 
by  the  amount  of  the  latent  heat  of  external  work  (/t  — /a)  z/. 


STORED  ENERGY.  27 

that  this  is  the  most  destructive  form  ot  boiler  on  the 
whole  list.  Its  simplicity  and  its  strength  of  form  make 
it  an  exceedingly  safe  boiler,  so  long  as  it  is  kept  in 
good  order  and  properly  managed ;  but,  if  through 
phenomenal  ignorance  or  recklessness  on  the  part  of 
proprietor  or  attendant,  the  boiler  is  exploded,  the  con- 
sequences are  usually  exceptionally  disastrous. 

No.  2  was  a  "  Cornish "  boiler,  designed  by  the 
Author,  about  1 860,  and  set  to  be  fired  under  the  shell. 
It  was  6  feet  by  36,  and  contained  a  36-inch  flue.  The 
shell  and  flue  were  both  of  iron  ^J-inch  in  thickness. 
The  boiler  was  tested  up  to  60  pounds,  at  which  press- 
ure the  flue  showed  some  indications  of  alteration  of 
form.  It  was  strengthened  by  stay-rings,  and  the  boiler 
was  worked  at  30  pounds.  The  boiler  contained  about 
12  tons  of  water,  weighed  itself  7^  tons,  and  the 
volume  of  steam  in  its  steam  space  weighed  but  3 1  ^ 
pounds  The  stored  available  energies  were  about 
57,600,000  foot-pounds,  and  about  700,000  of  foot- 
pounds in  the  water  and  steam,  respectively,  a  total  of 
nearly  60,000,000.  This  was  sufficient  to  throw  the 
boiler  to  the  height  of  3,400  feet,  or  over  three-fifths  of 
a  mile. 

Comparing  this  with  the  preceding,  it  is  seen  that  the 
introduction  of  the  single  flue,  of  half  the  diameter  of 
the  boiler,  and  the  reduced  pressure,  have  reduced  the 
relative  destructive  power  to  but  little  more  than  one- 
sixth  that  of  the  preceding  form. 

No.  3  is  a  "  two-flue  "  or  Lancashire  boiler,  similar 
in  form  and  in  proportions  to  many  in  use  on  the 


28  STEAM  BOILER  EXPLOSIONS. 

steamboats  plying  on  our  Western  rivers,  and  which 
have  acquired  a  very  unenviable  reputation  by  their 
occasional  display  of  energy  when  carelessly  handled. 
That  here  taken  in  illustration  was  designed  by  the 
Author,  42  inches  in  diameter,  with  two  1 4-inch  flues  of 
JHj  iron,  and  is  here  taken  as  working  at  a  pressure,  as 
permitted  by  law,  of  150  pounds  per  square  inch.  It  is 
rated  at  35  horse-power,  but  such  a  boiler  is  often 
driven  far  above  this  figure.  The  boiler  contains  about 
its  own  weight,  3  tons,  of  water,  and  but  37  pounds  of 
steam.  The  stored  available  energy  is  83,000,000  foot- 
pounds, of  which  the  steam  contains  but  a  little  above 
five  per  cent.  An  explosion  would  uncage  sufficient 
energy  to  throw  the  boiler  nearly  2*/2  miles  high, 
with  an  initial  velocity  of  900  feet  per  second.  Both 
this  boiler  and  the  plain  cylinder  are  thus  seen  to  have 
a  projectile  effect  only  to  be  compared  to  that  of  ord- 
nance. 

No.  4  is  the  common  plain  tubular  boiler,  substan- 
tially as  designed  by  the  Author  at  about  the  same  time 
with  those  already  described.  It  is  a  favorite  form  of 
boiler,  and  deservedly  so,  with  all  makers  and  users  of 
boilers.  That  here  taken  is  60  inches  in  diameter,  con- 
taining 66  3 -inch  tubes,  and  is  15  feet  long.  The  speci- 
men here  chosen  has  850  feet  of  heating  and  30  feet  of 
grate  surface,  is  rated  at  60  horse-power,  but  is  often 
driven  up  to  75,  weighs  9,500  pounds,  and  contains 
nearly  its  own  weight  of  water,  but  only  21  pounds  of 
steam,  when  under  a  pressure  of  75  pounds  per  square 
inch,  which  is  below  its  safe  allowance.  It  stores 


STORED  ENERGY.  29 

51,000,000  foot-pounds  of  energy,  of  which  but  4  per 
cent,  is  in  the  steam,  and  this  is  enough  to  drive  the 
boiler  just  about  one  mile  into  the  air,  with  an  initial 
velocity  of  nearly  600  feet  per  second.  The  common 
upright  tubular  boiler  may  be  classed  with  No.  4. 

Nos.  5-8  are  locomotive  boilers,  of  which  drawings 
and  weights  were  furnished  by  the  builders.  They  are 
of  different  sizes  and  for  both  freight  and  passenger  en- 
gines. The  powers  are  probably  rated  low.  They 
range  from  15  to  50  square  feet  in  area  of  grate,  and 
from  875  to  1350  square  feet  of  heating  surface.  In 
weight  the  range  is  much  less,  running  from  2^  to  a 
little  above  3  tons  of  water,  and  from  20  to  30  pounds  of 
steam,  assuming  all  to  carry  125  pounds  pressure.  The 
boilers  are  seen  to  weigh  from  2*/£  to  3  times  as  much 
as  the  water.  These  proportions  differ  considerably 
from  those  of  the  stationary  boilers  which  have  been 
already  considered.  The  stored  energy  averages  about 
70,000,000  foot-pounds  and  the  heights  and  velocities  of 
projection  not  far  from  3000  and  500  feet;  although,  in 
one  case,  they  became  nearly  one  mile,  and  550  feet  re- 
spectively. The  total  energy  is  only  exceeded,  among 
the  stationary  boilers,  by  the  two-flued  boiler  at  150 
pounds  pressure. 

Nos.  9  and  10  are  marine  boilers  of  the  Scotch  or 
"  drum  "  form.  These  boilers  have  come  into  use  by 
the  usual  process  of  selection,  with  the  gradual  increase 
of  steam  pressures  occurring  during  the  past  generation 
as  an  accompaniment  of  the  introduction  of  the  com- 
pound engine  and  high  ratios  of  expansion.  The 


3o  STEAM  BOILER  EXPLOSIONS. 

selected  examples  are  designed  for  use  in  recent  ves- 
sels of  the  U.  S.  Navy.  The  dimensions  are  obtained 
from  the  Navy  Department,  as  figured  by  the  Chief 
Draughtsman,  Mr.  Geo.  B.  Whiting.  The  first  is  that 
designed  for  the  "  Nipsic,"  the  second  for  the  "  Des- 
patch." They  are  of  300  and  350  horse  power,  and 
contain,  respectively,  73,000,000  and  110,000,000  of 
foot-pounds  of  available  energy,  or  about  3,000  foot- 
pounds per  pound  of  boiler,  and  sufficient  to  give  a 
height  and  velocity  of  projection  of  3,000  and  above 
400  feet.  These  boilers  are  worked  at  a  lower  pressure 
than  locomotive  boilers ;  but  the  pressure  is  gradually 
and  constantly  increasing  from  decade  to  decade,  and 
the  amount  of  explosive  energy  carried  in  our  modern 
steam-vessels  is  thus  seen  to  be  already  equal  to  that  of 
our  locomotives,  and  in  some  cases  already  considerably 
exceeds  that  which  they  would  carry  were  they  sup- 
plied with  boilers  of  the  locomotive  type  and  worked  at 
locomotive  pressures.  The  explosion  of  the  locomo- 
tive boiler  endangers  comparatively  few  lives  and  sel- 
dom does  serious  injury  to  property,  outside  the  engine 
itself.  The  explosion  of  one  of  these  marine  boilers 
while  at  sea  would  be  likely  to  be  destructive  of  many 
lives,  if  not  of  the  vessel  itself  and  all  on  board. 

Nos.  II  and  12  are  boilers  of  the  old  types,  suc^  as 
are  still  to  be  seen  in  steamboats  plying  upon  the  hud- 
son  and  other  of  our  rivers,  and  in  New  York  harbor 
and  bay.  No.  1 1  is  a  return  tubular  boiler  having  a 
shell  ten  feet  in  diameter  by  23  feet  long,  2  furnaces 
each  7j£  feet  deep,  5  1 5-inch  and  2  9-inch  flues,  and  85 


STORED  ENERGY.  31 

return  tubes,  4^  inches  by  1 5  feet.  The  boiler  weighs 
25  tons,  contains  nearly  20  tons  of  water  and  70  pounds 
of  steam,  and  at  30  pounds  pressure  stores  92,000,000 
foot-pounds  of  available  energy,  of  which  2*/2  per  cent, 
resides  in  the  steam.  This  is  enough  to  hoist  the  boiler 
one-third  of  a  mile  with  a  velocity  of  projection  of  330 
feet  per  second.  The  second  of  these  two  boilers  is  of 
the  same  weight,  also  of  about  200  horse  power,  but 
carries  a  little  more  water  and  steam,  and  stores  104,000,- 
ooo  foot-pounds  of  energy,  or  enough  to  raise  it  1,900 
feet.  This  was  a  return-flue  boiler,  33  feet  long  and 
having  a  shell  8^  feet  in  diameter,  flues  8^  to  15 
inches  in  diameter,  according  to  location. 

The  "  sectional "  boilers  are  here  seen  to  have,  for 
250  horse-power  each,  weights  ranging  from  about 
35,000  to  55»ooo  pounds,  to  contain  from  15,000  to 
30,000  pounds  of  water  and  from  25  to  58  pounds  of 
steam,  to  store  from  1 10,000,000  to  230,000,000  foot- 
pounds of  energy,  equal  to  from  2,000  to  5,000  foot- 
pounds per  pound  of  boiler.  The  stored  available  en- 
ergy is  thus  usually  less  than  that  of  any  of  the  other 
stationary  boilers,  and  not  very  far  from  the  amount 
stored,  pound  for  pound,  by  the  plain  tubular  boiler, 
the  best  of  the  older  forms.  It  is  evident  that  their  ad- 
mitted safety  from  destructive  explosion  does  not  come 
from  this  relation,  however,  but  from  the  division  of 
the  contents  into  small  portions,  and  especially  from 
those  details  of  construction  which  make  it  tolerably 
certain  that  any  rupture  shall  be  local.  A  violent  ex- 
plosion can  only  come  of  the  general  disruption  of  a 


STEAM  BOILER  EXPLOSIONS. 


boiler  and    the    liberation  at  once   of  large   masses  of 
steam  and  water. 

8.  The  Energy  of  Steam  Alone,  as  stored  in  the 
boiler,  is  given  by  column  10  of  the  preceding  table. 
It  has  been  seen  that  it  forms  but  a  small  and  unim- 
portant fraction  of  the  total  stored  energy  of  the  boiler. 
The  next  table  exhibits  the  effect  of  this  portion  of  the 
total  energy,  if  considered  as  acting  alone. 

STORED   ENERGY   IN   THE   STEAM  SPACE   OF   BOILERS. 


Type. 

Energy, 
Total. 

Stored  in  Steam 
(ft.  Ibs.) 
per  Ib.  of  Boiler. 

Height  of 
Projection 

Initial 
Velocity, 
per  sec. 

z 

Plain  Cylinder  

676,693 

271 

271  ft. 

132  ft. 

3 

Two-flue  Cylinder     

42 

TCO" 

Plain  tubular  

1  08 

I5° 

e 

Locomotive  

1,483    806 

76 

•76 

fio" 

i 

ge 

9  ti 

it 

*£ 

86 

74 

i 

it 

K  • 

Scotch  Marine 

°3 

10 

II 

12 

J3 

Flue  and  Return  Tube  '..'.'.'. 
Water-tube   .  .  . 

2,316,392 

1,570,517 

1,643,854 

28 
29 
61 

i! 

28 
29 

59  , 
62 
42  u 
43  " 

14 

59 

15 



X.3"i377 

24 

24  * 

71 
39 

The  study  of  this  table  is  exceedingly  interesting,  if 
made  with  comparison  of  the  figures  already  given,  and 
with  the  facts  stated  above.  It  is  seen  that  the  height 
of  projection,  by  the  action  of  steam  alone,  under  the 
most  favorable  circumstances,  is  not  only  small,  insig- 
nificant indeed,  in  comparison  with  the  height  due  the 
total  stored  energy  of  the  boiler,  but  is  probably  en- 
tirely too  small  to  account  for  the  terrific  results  of  ex- 


THE  ENERGY  OF  STEAM  ALONE. 


33 


plosions  frequently  taking  place.  The  figures  are  those 
for  the  stored  energy  of  steam  in  the  working  boiler ; 
they  may  be  doubled,  or  even  trebled,  for  cases  of  low 
water  ;  they  still  remain,  however,  comparatively  insig- 
nificant. 

The  enormous  force  of  molecular  power,  even  when 
heat  is  not  added  to  reinforce  them,  is  illustrated  by 
the  often  described  experiments  of  an  artillery  officer  at 
Quebec*  and  others,  in  which  a  large  bombshell  is  filled 


FIG. 


EXPANSIVE  FORCE  OF  ICE. 


with  water,  tightly  plugged,  and  exposed  to  low  temper- 
atures. In  such  cases  the  expansive  force  exerted, 
when  freezing,  by  the  formation  of  ice  and  the  increase 
of  volume  accompanying  the  formation  of  the  crystals, 
either  drives  out  the  plug,  sometimes  projecting  it 
hundreds  of  yards  (Fig.  3),  or  actually  bursts  the  thick 
iron  case. 

In  the  more  familiar  cases  of  purposely  produced 
explosion,  the  expansion  is  caused  by  the  production  of 
great  quantities  of  gas  previously  in  solid  form.  The 

*  Phenomena  of  Hunt  :  Cazin. 


34  STEAM  BOILER  EXPLOSIONS. 

violence  of  the  familiar  explosives  as  used  in  ordnance, 
in  mining  operations,  is  commonly  due  to  this  combined 
effect  of  heat  and  chemical  action,  occurring  by  the 
sudden  action  of  powerful  forces.  In  the  steam-boiler 
explosion,  mighty  forces  previously  long  held  in  subjec- 
tion, finally  overcome  all  resistance,  and  their  sudden 
application  to  external  bodies  constitute  the  disaster. 

9.     Explosion  and  Bursting  are  terms   which,    as 
often  technically  used  by  the  engineer,  represent  radi- 


FIG.  4.— AN  EXPLOSION. 

cally  different  phenomena.  The  explosion  of  a  steam- 
boiler  is  sudden  and  violent  disruption,  permitting  the 
stored  heat-energy  of  the  enclosed  water  and  steam  to 
be  expended  in  the  enormously  rapid  expansion  of  its 
own  mass,  and,  often,  in  the  projection  of  parts  of  the 
boiler  in  various  directions  with  such  tremendous  power 
as  to  cause  as  great  destruction  of  life  and  property  as  if 
the  explosion  were  that  of  a  powder-magazine.  The 


EXPLOSION  AND  BURSTING.  35 

bursting  of  a  boiler  is  commonly  taken  to  be  the  rup- 
ture, locally,  of  the  structure,  by  the  yielding  of  its 
weakest  part  to  a  pressure  which,  at  the  moment,  may 
not  be  deemed  excessive,  but  which  is  too  great  for  the 
weakened  spot.  The  collapse  of  a  flue  is  a  form  of 
rupture  which  is  ordinarily  considered  as  of  the  second 
class.  With  high  steam-pressure,  the  bursting,  or  the 
collapse,  of  a  flue,  may  occur  with  a  loud  report,  and 
may  even  cause  some  displacement  of  the  boiler ;  but  it 
is  not  generally  termed  an  explosion  where  the  boiler  is 
simply  upturned  and  is  not  torn  into  separated  pieces. 
There  is,  however,  no  real  boundary,  and  the  one 
grades  into  the  other,  with  no  defined  line  of  demarka- 
tion. 

It  occasionally  happens  that  an  explosion  takes  place 
with  such  extraordinary  violence  and  destructive  effect 
that  it  has  been  thought  best,  especially  by  French 
writers,  to  class  it  by  itself,  and  it  is  denoted  a  detonant 
or  fulminant  explosion,  "explosion  fulminante"  In 
such  cases,  the  report  is  like  that  of  an  enormous  piece 
of  ordnance ;  the  boiler  is  often  rent  into  many  parts, 
or  even  completely  broken  up  as  if  by  dynamite ;  and 
surrounding  objects  are  destroyed  as  if  by  the  discharge 
of  a  park  of  artillery. 

In  any  steam-boiler,  there  may,  at  any  time,  exist  a 
state  of  equilibrium  between  the  resisting  power  of  the 
boiler  and  the  steam-pressure.  In  ordinary  working, 
the  latter  is  far  within  the  former,  but  as  time  passes, 
the  limiting  condition  is  gradually  approached,  and,  in 
every  explosion,  the  line  is  passed.  The  pressure  may 


,5  STEAM  BOILER  EXPLOSIONS. 

rise  until  the  limit  of  strength  is  attained ;  or  the  resist- 
ing power  of  the  boiler  may  decrease  to  the  limit ;  in 
either  case,  the  passage  of  the  line  is  marked  by  explo- 
sion or  a  less  serious  method  of  yielding. 

10.  The  Causes  of  Boiler  Explosions  are  numer- 
ous, but  are  usually  perfectly  well  understood.  Where 
uncertainty  exists,  it  is  probably  the  fact  that,  were  the 
cause  ascertained,  it  would  be  found  to  be  simple  and 
well  known.  It  is,  nevertheless,  true  that  some  author- 
ities, including  a  few  experienced  and  distinguished 
members  of  the  engineering  profession,  believe  that 
there  are  causes,  at  once  obscure  and  of  great  potency  and 
energy,  which  are  not  yet  satisfactorily  understood.  In 
this  work,  the  many  causes  to  which  explosions  are,  by 
various  practitioners  and  writers,  attributed,  may  be 
divided  into  the  known,  the  probable,  the  possible,  the 
improbable,  and  the  impossible  and  absurd. 

To  the  first  class  belong  the  general  and  fairly  uniform 
weakness  of  boilers  as  compared  with  the  steam-press- 
ure carried  ;  the  sticking  of  safety  valves,  and  the  thou- 
sand and  one  other  causes  having  their  origin  in  the 
ignorance,  the  carelessness,  or  the  utter  recklessness  of 
the  designer,  the  builder,  or  the  attendants  entrusted 
with  their  management.  To  this  class  may  be  assigned 
the  causes  of  by  far  the  greater  proportion  of  all  explo- 
sions; and  the  Author  has  sometimes  questioned  whether 
this  category  may  not  cover  absolutely  all  such  catastro- 
phes. To  the  second  class  may  be  assigned  "low 
water,"  a  cause  to  which  it  was  once  customary  to  attri- 
bute nearly  all  explosions,  but  which  is  known  to  be 


THE   CAUSES  OF  BOILER  EXPLOSIONS.  37 

seldom  operative,  and  so  seldom  that  some  authorities 
now  question  the  possibility  of  its  action  at  all.*  Among 
the  possible  causes,  acting  rarely  and  under  peculiar 
conditions,  the  Author  would  place  the  overheating  of 
water,  and  the  storage  of  energy  in  excess  of  that  in 
the  liquid  at  the  temperature  due  the  existing  pressure  ; 
the  too  sudden  opening  of  the  throttle-valve,  or  the 
safety-valve,  producing  primingand shock;  thespheroidal 
state  of  water;  and  perhaps  other  phenomena.  The 
improbable  include  the  latter,  however.  The  action  of 
electricity,  a  favorite  idea  with  the  uninformed,  may  be 
taken  as  an  example  of  the  impossible  and  absurd. 
The  actual  causes  of  a  vast  majority  of  boiler  explosions 
are  now  determined  by  skilled  engineers,  inspectors  and 
insurance  experts ;  and  it  is  by  them  generally  supposed 
that  no  so-called  "  mysterious "  causes  exist,  in  the 
sense  that  they  are  phenomena  beyond  the  present 
range  of  human  knowledge  and  scientific  investigation. 

All  recent  authorities  agree  in  attributing  boiler-ex- 
plosions, almost  without  exception,  to  one  or  another  of 
the  following  general  classes  of  causes,  and  the  Author 
is  inclined  to  make  no  exception  : 

(i.)  Defective  design :  resulting  in  weakness  of  shell, 
of  flues,  or  of  bracing  or  staying;  in  defective  circula- 
tion; faulty  arrangement  of  parts;  inefficiency  of  pro- 
vision for  supplying  water  or  taking  off  steam  ;  and  de- 
fects in  arrangement  leading  to  strains  by  unequal  ex- 

*  See  opinion  of  Mr.  J.  M.  Allen,  Sibley  College  Lecture,  Sci.  Am. 
Supplement,  Feb.  19,  1887,  p.  9272. 


3  8  STEAM  BOILER  EXPLOSIONS. 

pansion,    and   other    matters   over  which   the  designer 
had  control. 

(2.)  Malconstruction:  including  choice  of  defective 
or  improper  material ;  faulty  workmanship  ;  failure  to 
follow  instructions  and  drawings  ;  omissions  of  stays  or 
braces. 

(3.)  Decay  of  the  structure  with  time  or  in  conse- 
quence of  lack  of  care  in  its  preservation;  local  defects 
due  to  the  same  cause  or  to  some  unobserved,  or  con- 
cealed leakage  while  in  operation. 

(4.)  Mismanagement  in  operation,  giving  rise  to  ex- 
cessive pressure  ;  low  water ;  or  the  sudden  throwing 
of  feed-water  on  overheated  surfaces ;  or  the  produc- 
tion of  other  dangerous  conditions ;  or  failure  to  make 
sufficiently  frequent  inspection  and  test,  and  thus  to 
keep  watch  of  those  defects  which  grow  dangerous 
with  time. 

Weakness  of  boiler  or  over-pressure  of  steam  are  the 
usual  immediate  causes  of  explosions. 

It  has  often  been  suggested  that  the  most  destructive 
boiler-explosions  may  be  attributable  to  electricity  and 
may  illustrate  the  effect  of  an  unfamiliar  form  of  light- 
ning. Such  hypotheses  are,  however,  absurd.  No  stor- 
age and  concentration  of  electricity  could  be  produced 
in  a  vessel  composed  of  the  best  of  conducting  ma- 
terials and  inclosing  a  mass  of  fluid  incapable  of  causing 
electrical  currents,  either  great  or  small,  under  the  con. 
ditions  observed  in  the  steam-boiler.  The  production 
of  electricity,  seen  in  Armstrong's  experiments,  a  phe- 
nomenon sometimes  thought  to  support  this  theory,  is 


THE   CAUSES  OF  BOILER  EXPLOSIONS. 


39 


simply  the  result  of  the  friction  of  a  moving  jet  of 
steam  on  the  nozzle  from  which  it  issued,  and  presents 
not  the  slightest  reason  for  supposing  that  the  elec- 
trical hypothesis  of  the  origin  of  boiler-explosions  have 
any  basis  of  fact 

Professor  Faraday,  in  a  report  to  the  British  Board  of 
Trade,  May,  1859,  states  his  belief  in  the  absurdity  of 
the  idea  that  the  water  within  a  steam-boiler  may  be- 
come decomposed  and  the  explosion  of  a  mixture  of 
gasses  so  produced  may  burst  a  boiler.  *  *  *  *  "  As 
respects  the  decomposition  of  the  steam  by  the  heated 
iron,  and  the  separation  of  hydrogen,  no  new  danger  is 
incurred.  Under  extreme  circumstances,  the  hydrogen 
which  could  be  evolved  would  be  very  small  in  quantity, 
would  not  exert  greater  expansive  force  than  the  steam, 
and  would  not  be  able  to  burn  with  explosion,  and 
probably  not  at  all  if  it  met  the  steam,  escaping  through 
an  aperture  into  the  air,  or  even  into  the  fireplace." 

Decomposition  cannot  occur  in  the  steam-boiler,  or- 
dinarily, and  if  it  were  to  happen  in  consequence  of 
low  water  and  overheated  plates,  no  oxygen  could  re- 
main free  to  explosively  combine  with  it. 

A  half  century  ago,  M.  Arago,  in  writing  of  steam 
boiler  explosions,*  asserted  "  that  no  cause  of  explosion 
exists  which  cannot  be  avoided  by  means  at  once  sim- 
ple and  within  reach  of  every  one."  A  committee  of  the 
Franklin  Institute,  in  1830,  asserted t  of  boiler-explo- 

*  Mem.  Roy.  Acad.  Sci.,  Inst.  France  ;  xxL 
t  Journal  Franklin  Institute,  1830. 


40  STEAM  BOILER  EXPLOSIONS. 

sions  that  "  they  proceed,  in  most  cases,  from  defective 
machinery,  improper  arrangement  or  distribution  of 
parts,  or  finally,  from  carelessness  in  management." 
These  conclusions  are  fully  justified  by  all  later  experi- 
ence, and  it  is  now  admitted  by  all  accepted  authorities 
that  a  careful  examination  and  study  of  the  facts  of  the 
case  will  almost  invariably  enable  the  experienced  en- 
gineer to  determine  the  origin  of  the  disaster.  It  fol- 
lows that  it  is  perfectly  practicable  to  so  design,  con- 
struct, and  manage  steam-boilers  that  there  shall  be  ab- 
solutely no  danger  of  explosion. 

That  the  great  majority,  if  not  all,  explosions  are  due 
to  preventible  causes  was  thus  very  early  recognized. 
President  Andrew  Jackson,  in  his  fifth  Annual  Message 
to  Congress,  Dec.  3d,  1883,  says: 

"  The  many  distressing  accidents  which  have  of  late 
occurred  in  that  portion  of  our  navigation  carried  on  by 
the  use  of  steam-power,  deserves  the  immediate  and  un- 
remitting attention  of  the  constituted  authorities  of  the 
country.  The  fact  that  the  number  of  those  fatal  dis- 
asters is  constantly  increasing,  notwithstanding  the  great 
improvements  which  are  everywhere  made  in  the  ma- 
chinery employed,  and  the  rapid  advances  which  have 
been  made  in  that  branch  of  science,  show  very  clearly 
that  they  are  in  a  great  degree  the  result  of  criminal 
negligence  on  the  part  of  those  to  whose  care  and  at- 
tention the  lives  and  property  of  our  citizens  are  so  ex- 
tensively entrusted. 

"That  these  evils  may  be  greatly  lessened,  if  not  sub- 
stantially removed,  by  means  of  precautionary  and  penal 


THE   CAUSES   OF  BOILER  EXPLOSIONS.  41 

legislation,  seems  to  be  highly  probable  ;  so  far,  there- 
fore, as  the  subject  can  be  regarded  as  within  the  con- 
stitutional purview  of  Congress,  I  earnestly  recommend 
it  to  your  prompt  and  serious  attention." 

Modern  experience  and  recent  investigation  confirm 
these  statements. 

The  United  Society  of  Boiler-makers  express  the 
general  opinion  of  engineers  on  this  subject  in  the  follow- 
ing language :  * 

"  If  masters  who  manufacture  boilers  and  those  who 
use  them  would  be  more  judicious  in  their  selection  of 
boilers  made  of  the  best  materials  and  after  the  most 
approved  principles,  we  should  rarely  listen  to  the  hor- 
rifying details  of  boiler  explosions." 

There  are,  nevertheless,  certain  defects  inherent  in 
the  type  which  involve  some  risks  notwithstanding 
the  facts  that  good  design,  good  construction,  and  com- 
petent management  may  minimize  them.  Such  are  the 
risks  involved  in  stayed  surfaces  such  as  are  often  illus- 
trated in  locomotive  fire-boxes,  the  liability  of  the  seam 
of  the  shell-boiler  to  crack  along  the  rivet-line  under 
the  lap,  out  of  reach  of  inspection,  the  cracking  of  the 
tubes  in  water-tube  boilers,  etc. 

In  common  practice,  to-day,  however,  the  specifica- 
tions are  usually  so  explicit  and  so  detailed  that  only 
good  materials  will  be  employed,  well-settled  forms 
and  proportions  will  be  adopted,  and  construction  will 
be  satisfactory.  For  compliance  with  specifications  the 
inspector  for  the  purchaser  must  be  responsible. 

n.  The  Statistics  of  Explosions  have  been  very 

*  London  Engineer,  July  29,  1870,  p.  77. 


4 2  STEAM  BOILER   EXPLOSIONS. 

carefully  collected  for  many  years  in  some  European 
communities,  notably  in  France,  and  are  now  given  for 
the  United  States  in  very  reliable  form  by  inspectors, 
governmental  and  private,  who  are  thoroughly  familiar 
with  the  subject.  The  following  is  a  list  reported  for 
the  year  1885 

CLASSIFIED  LIST  OF  BOILER  EXPLOSIONS. 


JANUARY. 

FEBRUARY. 

~ 

y 
< 

^ 

APRIL. 

< 

ti 
•£ 

S 

—  , 

2 

AUGUST. 

SEPTEMBER. 

OCTOBER. 

NOVEMBER. 

DECEMBER. 

TOTAL  PER  CLASS. 

Saw-mills  and  wood-working  shops 

" 

- 

" 

3 

- 

Steamboats,  tugs,  etc  

4 

• 

a 

1 

yCi 

Portables,  hoisters  and  agricultural  engines  
Mines,  oil  wells,  collieries,  etc  

i 

2 

4 

2 

3 

9 

2 

1  6 

Paper-mills,  bleachers,  digesters,  etc  

5 

3 

^ 

Roliing-mills  and  iron-works  

10 

Distilleries,  breweries,  sugar-houses,  dye-houses, 
rendering  establishments,  etc 

.0 

1 

3 

! 

Textile   manufactories  

• 

*  • 

"-* 

1 

1 

Miscellaneous 

18 

J 

-' 

3 

"* 

Total  per  month  

Persons  killed,  total  220  per  month  
Persons  injured,  total  288  per  month.. 

2  4 

35 

22 

3o 

20 
28 

c 

9 

18 
3~ 

*4 
6 

21 

II 
21 

ii 
13 

1C) 

4' 

34 

22 

31 
21 

Boilers  used  in  saw-mills  are  most  frequently  ex- 
ploded, presumably  because  of  the  cheapness  of  their 
construction,  and  the  unskillfulness  exhibited  in  their 
management;  boilers  in  mines  are  next  in  number  o{ 
casualities.  Factory-boilers  explode  with  comparative  in- 
frequency.  In  the  United  States,  according  to  the  best 


THE   STATISTICS   OF  EXPLOSIONS. 


43 


estimates  which  the  Author  has  been  able  to  make, 
about  one  boiler  in  10,000  explodes  among  those  which 
are  regularly  inspected  and  insured,  and  ten  times  that 
proportion  among  uninspected  and  uninsured  boilers. 
According  to  Reiche,*  in  Great  Britain,  recently,  one 
explosion  has  occurred  in  every  500  boilers  not  under 
inspection  ;  in  Prussia,  one  in  1,000  under  state  control 
and  inspection;  and  in  Great  Britain  one  in  10,000 
boilers  in  charge  of  the  private  inspection  companies. 
Explosions  might  become  almost  unknown  were  a 
proper  system  of  inspection  and  compulsory  repair  in- 
troduced. 

In  Great  Britain  the  proportion  of  explosions  is 
much  less  than  in  the  United  States,  the  average  num- 
ber being  less  than  one- twentieth  of  one  per  cent,  and 
the  loss  of  life  about  three  to  every  two  explosions.  In 
Great  Britain,  as  in  the  United  States  and  elsewhere, 
the  majority  of  explosions  are  due  to  negligence. 

The  returns  of  boiler-explosions  in  Great  Britain  and 
the  United  States  show  that  not  only  in  number  but  in 
destructiveness  the  record  of  the  United  States  always 
exceeds  that  of  Great  Britain,  as  is  seen  in  the  following 
table. 


No.   Explosions. 

No.  Fatalities. 

No.  Persons  inj  d. 

1884. 

1885. 

1884. 

1885. 

1884. 

1885. 

Great  Britain  

36 
152 

43 

*55 

24 

254 

40 

220 

49 
261 

fa 

288 

United  States  

*  Anlage  und   Betrieb  der  Dampfkessel  ;    H.   v.    Reicbe ;   Leipzig, 
1876. 


44 


STEAM  BOIhER   EXPLOSIONS. 


No.    Kxplosions  per    Million 
Inhabitants. 

No.  Fatalities  per  Explosion. 

1884. 

1885. 

1884. 

!885 

Great    Britain  

I 

1.17 

.67 

•93 

United   States  

3 

3  °9 

1.67 

1.42 

The  causes  of  the  43  explosions  in  Great  Britain  are 
reported  to  have  been  : 

Cases. 

Deterioration  or  corrosion  of  boilers  and  safety-valves 20 

Defective  design  or  construction  of  boiler  or  fittings. «   u 

Shortness  of  water. t 4 

Ignorance  or  neglect  of  attendants. . .    4 

Miscellaneous , 4 


Total. 


43 


For  the  United  States  there  are  estimated  to  have 
been  dangerous  cases,  classified  thus : 


Causes. 


Deterioration  or  corrosion  of  boilers  and  safety- 
valves « . . . . 

Defective  design  or  construction  of  boiler  or 
fittings 

Shortness  of  water 

Ignorance  or  neglect  of  attendants 

Miscellaneous .  . 


Whole  No. 


130 
6,404 
6,928 


Dangerous 


2,957 

56 

983 

1.403 


THE    STATISTICS  OF  EXPLOSIONS. 


45 


The  following  are  two  classified  lists  of  defects  and 
causes  of  dangerous  conditions,  where,  in  one  case, 
over  6,000  boilers,  and  in  the  other  about  10,000,  are 
inspected  :  * 


Nature  of  Defects. 


Whole  Number. 


)angerous. 


Deposit  of  sediment 458 

Incrustation  and  scale 630 

Internal   grooving 20 

Internal  corrosion 155 

External  corrosion 346 

Broken,  loose,  and  defective  braces  and  stays.  205 

Defective  settings 178 

Furnaces  out  of  shape 248 

Fractured  plates 123 

Burned  plates 89 

Blistered  plates 254 

Cases  of  defective  riveting 1*649 

Defective  heads 30 

Leakage  around  tube  ends 974 

Leakage  at  seams 574 

Defective  water  guages 163 

Defective  blow-offs  3° 

Cases  of  deficiency  of  water 5 

Safety-valves  overloaded 29 

Safety-valves  defective  in  construction 42 

Defective  pressure-guages 238 

Boilers  without  pressure-guages 4 

Defective  hand-hole  plates 3 

Defective  hangers 13 

Defective  fusible  plugs I 

Total..               6,453 


33 
55 

16 
23 
39 
i? 

12 

65 
22 

i: 

187 

15 

331 

22 
27 

8 

2 

7 

7 

19 
o 

3 
o 

o 

927 


*'•  The  Locomotive,"  Dec.,  1884  ;  Feb.,   1902. 

v 


46  STEAM  BOILER  EXPLOSIONS. 

Nature  of  Defects.  Whole  Number.     Dangerous. 

Cases  of  deposit  of  sediment 14,109  731 

Cases  of  incrustation  and  scale 36, 137  986 

Cases  of  internal  grooving 2,284  ^53 

Cases  of  internal  corrosion lo-383  461 

Cases  of  external  corrosion 8, 135  532 

Defective  braces  and  stays 3>°35  680 

Settings  defective 4,986  363 

Furnaces  out  of  shape 5,5 12  249 

Fractured  plates 3, 802  632 

Burned  plates ....  4,691  477 

Blistered  plates !>379  39 

Defective  rivets 32.303  897 

Defective  heads 998  147 

Leakage  around  tubes 3!,925  3,1?1 

Leakage  at  seams 5?3°6  308 

Water-gauges  defective 3,39$  626 

Blow-offs  defective 2,465  702 

Cases  of  deficiency  of  water 393  123 

Safety-valves  overloaded 1, 180  438 

Safety-valves  defective 932  323 

Pressure-gauges  defective 5,284  361 

Boilers  without  pressure  gauges 163  163 

Unclassified  defects 9,047  52 


Totals 187,847         12,614 

It  is  seen  that  many  of  these  defects,  all  of  which  are 
dangerous  and  liable  to  cause  explosion,  are  of  very 
variable  frequency,  as,  for  example,  defective  riveting, 
which  is  more  tha,n  twice  as  common,  in  the  first  list,  as 
any  other  defect,  but  which  stands  number  three  in  the 
second ;  while  other  defects  are  of  quite  regular  occur- 
rence, as  the  presence  of  sediment  and  of  scale,  groov- 
ing, and  other  corrosion,  injured  plates  and  defective 
guages.  Sediment,  oxidation,  and  defective  workman- 
ship are  evidently  the  most  prolific  causes  of  danger ; 
and  unequal  expansion,  to  which  many  of  the  reported 
cases  of  leakage  are  attributable,  hardly  less  so. 


THEORIES  AND  METHODS.  47 

An  inspection  of  these  tables  plainly  shows  that  the 
causes  of  steam-boiler  explosions  are  commonly  perfectly 
simple  and  are  well  understood ;  and  a  person  familiar 
with  the  subject  usually  wonders  that  explosions  occur 
as  infrequently  as  they  do,  where  there  are  so  many 
sources  of  danger  and  where  so  little  intelligence  and 
care  is  exhibited  in  their  design,  construction,  and 
operation.  There  are,  however,  some  interesting  phe- 
.nomerta,  and  some  very  ingenious  theories  as  to  method 
of  liberation  of  the  enormous  stock  of  energy  of  which 
every  boiler  is  a  reservoir,  to  which  attention  may  well 
be  given. 

12.  Theories  and  Methods  of  explosions  due  to 
other  causes  than  simple  increase  of  steam-pressure  or 
decrease  in  strength  of  boiler,  and  of  such  accidents  as 
are  common  and  well  understood,  and  produce  the 
greater  number  of  disasters  of  the  class  here  studied, 
are  as  various  as  they  are  interesting.  The  vast  ma- 
jority of  all  boiler-explosions  have  been,  as  has  been 
seen,  found  to  be  due  to  causes  which  are  readily  de- 
tected and  are  the  simplest  and  most  obvious  possible. 
Here  and  there,  however,  an  explosion  takes  place 
which  is  so  exceptionally  violent,  or  which  occurs  under 
such  unusual  and  singular  conditions,  as  to  give  rise  to 
question  whether  some  peculiar  phenomenon  is  not  con- 
cerned in  bringing  about  so  extraordinary  a  result. 
Nearly  all  explosions  have  been  produced  either  by  a 
gradual  rise  in  pressure  until  the  resisting  power  of  the 
boiler  has  been  exceeded  and  an  extended  rupture  lib- 
erates the  stored  energy;  or  by  a  gradual  reduction 


4  8  STEAM  BOILER  EXPLOSIONS. 

of  the  strength  of  the  structure  until,  at  last,  it  is  insuf- 
ficient to  withstand  the  ordinary  working  pressure,  and 
a  general  yielding  leads  to  the  same  result.  Such  cases 
require  little  comment  and  no  explanation.  But  the 
rare  instances  in  which  a  sudden  development  of  forces 
far  in  excess  of  those  exhibited  in  regular  working 
have  been  believed  to  have  been  observed,  have  given 
rise  to  much  speculation,  to  many  ingenious  theories, 
and  to  an  immense  amount  of  speculation  and  miscon- 
ception on  the  part  of  those  who  are  unfamiliar  with 
science  and  without  experience  in  the  operation  of  this 
class  of  apparatus. 

Explosions  probably  always  occur  from  perfectly 
simple  and  easily  comprehended  causes,  are  always  the 
result  of  either  ignorance  or  carelessness,  and  are 
always  preventible  where  intelligence  and  conscientious- 
ness govern  the  design,  the  construction,  and  the  man- 
agement of  the  boiler.  A  well-designed  boiler,  properly 
proportioned  for  its  work  and  to  carry  the  working 
pressure,  well  built,  of  good  materials,  and  intelligently 
and  carefully  handled,  has  probably  never  been  known 
to  explode.  Explosions  probably  rarely  occur,  with 
either  a  gradually  increasing  pressure  of  steam,  or 
decreasing  strength  of  boiler  unless  the  strength  of  the 
structure  is  quite  uniform  ;  local  weakness  is  a  safety- 
valve  which  permits  a  "  burst "  and  insures  against  that 
more  general  disruption  ivhich  is  called  an  "  explosion." 
A  long  line  of  weakened  seam,  an  extended  crack,  or  a 
considerable  area  of  surface  thinned  by  corrosion  may 
lead  to  an  explosion  and  a  general  breaking  up  of  the 


THEORIES  AND  METHODS.  49 

whole  apparatus ;  but  any  minor  defect,  when  its  site  is 
surrounded  by  strong  parts,  will  not  be  likely  to  pro- 
duce that  result 

The  Method  of  Explosion  is,  in  the  great  major- 
ity of  cases,  the  opening  of  a  small  orifice  at  a  point  of 
minimum  strength,  with  outrush  of  water  or  steam,  or 
both,  the  rapid  extending  of  the  rupture  until  it  becomes 
so  great  and  the  operation  so  rapid  that,  no  time  being 
given  for  the  gradual  discharge  of  the  enclosed  fluids, 
the  boiler  is  torn  violently  apart  by  the  internal  unre- 
lieved pressure  and  distributed  in  pieces,  the  number  of 
which  is  determined  by  the  character  and  extent  of  the 
lines  or  areas  of  weakness.  The  violence  of  the  pro- 
jection of  the  detached  parts  depends  on  the  magnitude 
of  the  pressure  and  the  rapidity  with  which  disruption 
takes  place.  The  most  destructive  explosions  are  often 
distinguished  by  a  general  breaking  up  of  the  whole 
structure.  In  the  case  of  the  "  burst "  boiler,  the 
opening  is  of  limited  extent  and  the  contents  of  the 
boiler  are  discharged  without  tearing  it  in  pieces. 

"  Colburn's  Theory,"  to  be  presently  described,  is  an 
attempt  to  state  the  method  of  explosion  and  the  reasons 
therefor,  and  the  other  theories,  accepted  or  otherwise, 
usually  attempt  the  same  thing  for  general  or  special 
cases. 

13.  Clark  and  Colburn's  Theory  of  boiler-explo- 
sions has  been  accepted  as  a  "  working  hypothesis  >e  by 
many  engineers  and  has  some  apparent  foundation  in 
experimentally  ascertained  fact  This  theory  is  attri- 


50  STEAM  BOILER  EXPLOSIONS. 

buted  to  Mr.  Zerah  Colburn,*  but  was  probably,  as 
stated  by  Mr.  Colburn  himself,  original  with  Mr.  D.  K. 
Clark,  who  suggests  that  a  rupture  initiated  at  the 
weakest  part  of  a  boiler,  above  or  near  the  water-line, 
may  be  extended  and  an  explosion  precipitated  by  the 
impact  of  a  mass  of  water  carried  toward  it  by  the 
sudden  outrush  of  a  quantity  of  steam,  precisely  as  the 
"  water-hammer "  observed  so  frequently  in  steam- 
pipes  causes  an  occasional  rupture  of  even  a  sound  and 
strong  pipe.  In  fact,  many  instances  have  been  observed 
in  which  the  rent  thus  presumed  to  have  been  produced 
has  extended  not  only  along  lines  of  reduced  section, 
but  through  solid  iron  of  full  thickness  and  of  the  best 
quality.  It  is  thus  that  Mr.  Clark  would  account  for 
the  shattering  and  the  deformation  of  portions  of  the 
disrupted  boiler  which  are  often  the  most  striking  and 
remarkable  phenomena  seen  in  such  instances. 

Colburn  suggests  that  the  explosion,  in  such  cases, 
although  seemingly  instantaneous,  may  actually  be  a 
succession  of  operations,  three  or  four,  at  least,  as  the 
following : 

(i.)  The  initial  rupture  under  a  pressure  which  may 
be,  and  probably  often  is,  the  regular  working  pressure; 
or  it  may  be  an  accidentally  produced  higher  pressure ; 
the  break  taking  place  in  or  so  near  the  steam-space  that 
ai-  immediate  and  extremely  rapid  discharge  of  steam 
and  water  may  occur. 


*Steam  Boiler  Explosions :   Zerah  Colburn.     London  :   John  Weale 
1860. 


CLARK  AND  COLB URN'S  THEORY.  51 

(2.)  A  consequent  reduction  of  pressure  in  the 
boiler,  and  so  rapid  that  it  may  become  considerable 
before  the  inertia  of  the  mass  of  water  will  permit  its 
movement. 

(3.)  The  sudden  formation  of  steam  in  great  quan- 
tity within  the  water  and  the  precipitation  of  heavy 
masses  of  water,  with  this  steam,  toward  the  opening, 
impinging  upon  adjacent  parts  of  the  boiler  and  break- 
ing it  open,  causing  large  openings  or  extended  rents, 
and,  often,  shattering  the  whole  structure  into  numerous 
pieces. 

(4.)  The  completion  of  the  vaporization  of  the  now 
liberated  mass  of  water  to  such  extent  as  the  reduction 
of  the  temperature  may  permit,  and  the  expansion  of 
the  steam  so  formed,  projecting  the  detached  parts  to 
distance  depending  on  the  extent  and  velocity  of  this 
action. 

This  series  of  phenomena  may  evidently  be  the 
accompaniment  of  any  explosion,  to  whatever  cause  the 
initial  rupture  may  be  due.  One  circumstance  lending 
probability  to  this  theory  is  the  rarity  of  explosions 
originating  in  the  failure  of  "water-legs"  or  other  parts 
situated  far  below  the  water-line.  This  occasionally  hap- 
pens, as  was  seen  some  time  ago  at  Pittsburgh,  in  the 
explosion  of  a  vertical  boiler,  caused  by  a  crack  in  the 
water-leg;  but  it  is  almost  invariably  observed  that 
explosions  occur  where  long  lines  of  weakened  metal, 
defective  seams,  or  of  "  grooving "  extend  nearly  or 


52  STEAM  BOILER  EXPLOSIONS. 

quite  to  the  steam  space.*  A  local  defect  well  below 
the  water-line  would  usually  simply  act  as  a  safety-valve, 
discharging  the  contents  of  the  boiler  without  explosion. 

14.  Corroboratory  Evidence  has  been  here  and  there 
found.  Lawson's  experiments,  and  those  of  others,  as 
well  as  many  accidental  explosions,  have  supplied  evi- 
dence somewhat,  but  not  absolutely,  corroboratory  of 
the  Clark  and  Colburn  theory.  Mr.  D.  T.  Lawson,  hav- 
ing become  convinced  of  the  truth  of  the  Clark  and 
Colburn  theory,  further  conceived  the  idea  that  the 
opening  and  sudden  closing  of  the  throttle  or  the  safety- 
valve  might  cause  precisely  the  same  succession  of 
phenomena,  and  lead  to  the  explosion  of  boilers ;  the 
opening  starting  the  current,  and  the  closing  of  the  valve 
producing  impact  that  may  disrupt  the  boiler.  To  test 
the  truth  of  his  hypothesis,  he  made  a  number  of  experi- 
ments, and  succeeded  in  exploding  a  new  and  strong 
boiler  at  a  pressure  far  below  that  which  it  had  immedi- 
ately before  safely  borne.  As  a  preventive,  he  proposed 
the  introduction  of  a  perforated  sheet-iron  diaphragm, 
dividing  the  interior  of  the  boiler  at  or  near  the  water- 
line,  the  expectation  being  that  it  would  check  the 
action  described  by  Colburn  and  prevent  that  percussive 
effect  to  which  explosion  was  attributed  by  him,  and 
also  that  it  would  be  found  to  possess  some  other  advan- 
tages. 

The  experiments  were  made  at  Munhall,  near   Pitts- 

*  The  "  Westfield  "  explosion  illustrates  this  case.  Jour.  Frank.  Inst., 

1875. 


CORROBORA  TOR  Y  E  VIDENCE.  5  3 

burgh,  Pa.,  in  March,  1882,  the  boiler  being  of  th' 
cylindrical  variety,  30  inches  (76  cm.)  in  diameter  and 
72^  feet  (2.06  m.)  in  length,  of  iron  3-1 6  inch  (0.48  cm.^ 
in  thickness.  Its  strength  was  estimated  at  430  pound: 
per  square  inch  (28^3  atmos.)  It  was  fitted  with  a  dia- 
phragm, as  above  described. 

After  some  preliminary  tests,  the  folio  wing  were  made,* 
the  valve  being  opened  at  intervals  and  suddenly  closed 
again  at  the  pressures  given  below,  as  taken  from  the 
log.  A  steam- guage  was  attached  to  the  boiler  above 
and  another  below  the  diaphragm.  The  boiler  contained 
1 8  inches  of  water.  Steam  was  generated  slowly,  and 
when  the  pressure  had  reached  50  pounds,  operating 
the  discharge  valve  began,  with  the  following  results : 

*  Report  of  U.  S.  Inspectors  to  the  Secretary  of  the  Treasury,  Mch, 
23d    1882. 


54 


STEAM  BOILER  EXPLOSIONS. 


Steam  pressure 
at  which  dis- 
charge valve  was 
raised. 

Steam-gau^e  above 
diaphragm. 

Steam-gauge  below  the 
diaphragm. 

Needle  fell 
below. 

Needle  rose 
above. 

Needle  fell 
below. 

Needle  rose 
above 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

50 

7 

3 

3 

00 

80 

10 

7 

4 

00 

100 

12 

7 

5 

3 

125 

15 

15 

8 

4 

*5o 

20 

20 

8 

7 

175 

15 

23 

10 

10 

200 

20 

20 

15 

oo 

225 

30 

20 

12 

00 

230 

40 

30 

IO 

00 

250 

25 

2O 

10 

00 

275 

30 

25 

15 

oo 

300 

40 

35 

15 

00 

When  the  pressure  in  the  boiler  reached  300  pounds 
to  the  square  inch,  it  was  decided  that  the  boiler  had 
been  sufficiently  tested,  and  the  boiler  was  emptied  and 
inspected.  The  rivets,  seams,  and  all  the  other  parts  of 
the  boiler  were  examined,  and  no  strain,  rupture,  or 
weakness  was  discovered.  The  diaphragm  was  then  cut 
out,  leaving  the  flanges  riveted  to  the  sides  of  the  shell 
and  across  the  heads.  The  boiler  was  then  again  tested, 
with  the  following  results : 


CORROBORA  TOR  Y  E  V2DENCE. 


55 


Steam  pressure 
at  which  dis- 
cha  rge  valve  was 
raised. 

Steam-guage  attached  to  the 
boiler  in  the  steam-space. 

Steam-guage  attached  to  the 
boiler  in  water-space. 

Needle  fell 
below. 

Needle  rose 
above. 

Needle  fell 
below. 

Needle  rose 
above. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

100 

3 

oo 

3 

00 

125 

2 

oo 

3 

oo 

150 

5 

oo 

5 

00 

175 

4 

2 

3 

2 

200 

5 

00 

5 

00 

210 

3 

00 

3 

00 

225 

5 

00 

3 

oo 

235 

Exploded. 

When  the  discharge- valve  was  opened  at  235  pounds 
pressure,  it  caused  the  explosion  of  the  boiler;  it  was 
blown  into  fragments.  The  iron  was  torn  and  twisted 
into  every  conceivable  shape ;  strips  of  various  sizes  and 
proportions  were  found  in  all  directions.  The  boiler 
did  not  always  tear  at  the  seams,  but  principally  in  the 
solid  parts  of  the  iron. 

At  the  time  of  the  explosion  the  water-line  was 
higher  than  during  the  test  immediately  preceding. 
At  an  earlier  privately  made  experiment,  as  reported 
by  the  same  investigator,  an  explosion  of  a  new  boiler 
had  been  similarly  produced  at  one-half  the  pressure 
which  it  had  been  estimated  that  the  boiler  might  sus- 
tain. A  significant  fact  exhibited  in  the  record  is  the 
enormously  greater  fluctuation  of  pressure  in  the  boiler 


5 6  STEAM  BOILER  EXPLOSIONS. 

during  the  first  than  during  the  second  trial,  and  the 
difference  in  the  amount  of  that  fluctuation  above  and 
below  the  diaphragm. 

The  result  of  this  action  in  the  ordinary  operation  of 
the  safety-valve  or  of  the  throttle-valve  is  apparently 
extremely  uncertain.  Many  explosions  have  occurred 
under  such  circumstances  as  would  seem  to  indicate  the 
probability  of  the  action  described  having  been  their 
cause,  the  disaster  following  the  opening  of  safety- 
valve,  or  of  the  throttle  at  starting  the  engines. 

On  the  other  hand,  these  operations  are  of  constant 
occurrence  and  with  weak  and  dangerous  boilers,  and 
such  explosions  are,  nevertheless,  extremely  rare.  The 
Author,  while  officially  engaged  in  attempting  the  experi- 
mental production  of  boiler-explosions,  as  a  member  of 
the  U.  S.  Board  appointed  for  that  purpose,  made  nu- 
merous experiments  of  this  nature,  but  never  succeeded 
in  producing  an  explosion.  The  danger  would  seem  to 
be,  fortunately,  less  than  it  might  be,  judging  from  the 
above.  The  introduction  of  feed  water  into  the  steam- 
space  of  boilers,  producing  sudden  removal  of  pressure 
from  the  surface  of  the  water  is  sometimes  supposed  to 
have  caused  explosions.  The  explosion  of  a  battery  of 
several  boilers  simultaneously — not  an  infrequent  case — 
is  supposed  to  be  attributable  to  the  action  described 
above,  following  the  rupture  of  some  one  of  the  set. 

Mr.  J.  G.  Heaffman,  writing  in  1867,*  anticipated 
Mr.  Lawson's  idea,  and,  after  describing  an  explosion  of 

*  Journal  of  Assoc.  of  German  Engineers,  1867  ;   Iron  Age,  1867. 


CORROBORATORY  EVIDENCE.  57 

a  bleaching  boiler,  to  which  the  steam  was  supplied 
from  a  separate  steam-boiler,  attributed  the  catastrophe 
to  impact  of  water  against  the  shell,  or  the  accidental 
production  of  an  opening  at  the  manhole,  and  asserts 
that  explosions  thus  occur  not  only  from  excess  of 
pressure,  but  also  from  shock.  He  further  states  that, 
in  accordance  with  a  request  made  by  the  Association 
of  German  Engineers,  a  commission  of  the  Breslau 
Association  experimenting  with  a  small  glass  boiler, 
found  that  when  the  escape-pipes  are  only  gradually 
opened,  and  the  steam  allowed  gradually  to  escape,  the 
generation  of  steam  quietly  continues  and  the  water  re- 
mains tranquil.  But  if  the  valve  is  quickly  opened, 
steam  bubbles  suddenly  form  all  through  the  water,  and 
rising  to  the  surface,  produce  violent  commotion.  In 
one  of  these  experiments  it  was  his  duty  to  watch  the 
manometer,  while  another  person  quickly  opened  the 
valve  to  allow  the  steam  to  escape.  As  soon  as  the 
valve  was  opened  the  pressure  fell  3  Ibs.,  but  imme- 
diately again  began  to  rise  and  the  boiler  exploded. 
Where  it  had  been  in  contact  with  the  water  it  was 
shattered  to  powder,  which  lay  around  like  fine  sand. 
Of  the  entire  boiler  only  a  few  small  pieces  of  the  size 
of  a  dollar  were  left.  Afterward  they  constructed  a 
similar  glass  boiler  with  a  cylinder  7  inches  in  diameter, 
and  9  inches  in  length,  and  to  the  ends  metal  heads 
were  fastened  ;  in  the  heads  were  pipes  for  leading  in 
the  steam.  By  means  of  a  force  pump  the  boiler  was 
filled  with  boiling  water,  the  valve  being  left  open 
meanwhile,  in  order  that  its  sides  might  become  evenly 


5  8  STEAM  BOILER  EXPLOSIONS. 

heated.  Then  half  the  water  was  drawn  off  and  air  let 
in,  and  afterward  more  boiling  water  forced  in,  so  that 
the  air  was  compressed,  until  the  boiler  exploded  at  a 
pressure  of  15  atmospheres. 

The  report  was  not  nearly  as  loud  as  at  the  former 
explosion,  which  took  place  at  a  pressure  of  only  3  at- 
mospheres, and  the  glass  was  only  broken  into  several 
pieces.  This,  Mr.  Heaffman  considers,  proves  that 
the  action  of  the  water  on  the  boiler  is  such  as  would 
be  produced  by  exploding  nitro-glycerine  in  the  water. 

He  goes  on  to  state  that,  in  bleacheries,  dye  works, 
etc.,  the  habit  often  prevails  of  suddenly  opening  the 
steam-cocks,  thus  endangering  the  boiler.  He  does  not 
assert  that  every  time  a  cock  is  suddenly  opened  an 
explosion  must  follow ;  but  that  it  may  take  place 
experience  has  shown.  In  the  experiments  above 
described  they  had  many  times  opened  the  glass  boiler 
without  causing  an  explosion ;  with  the  second  boiler, 
too,  they  had  done  so  without  being  able  to  bring  about 
explosion  ;  both  with  high  and  low  pressure.  In  the 
former  class  of  explosions,  the  steam  shatters,  twists  and 
contorts  the  parts  in  an  instant. 

"  Water-hammer "  has,  by  the  bursting  of  steam- 
pipes,  by  a  process  somewhat  closely  related  to  that 
described  by  Clark  and  Colburn,  sometimes  caused 
fatal  injury  to  those  near  at  the  instant  of  the  accident. 
This  is  a  phenomenon  which  has  long  been  familiar  to 
engineers,  and  the  Author  has  been  cognizant  of  many 
illustrations,  in  his  own  experience,  of  its  remarkable 
effects,  and  has  sometimes  known  of  almost  as  serious 


CORROBORATORY  EVIDENCE.  59 

losses  of  life  as  from  boiler-explosions.  It  is  rarely  the 
cause  of  serious  loss  of  property. 

When  a  pipe  contains  steam  under  pressure,  and  has 
introduced  into  it  a  body  of  cold  water,  or  when  a 
cold  pipe,  containing  water,  is  suddenly  filled  with 
steam,  the  contact  of  the  two  fluids,  even  when  the 
water  is  in  very  small  quantities,  results  in  a  sudden 
condensation  which  is  accompanied  by  the  impact  of 
the  liquid  upon  the  pipe  with  such  violence  as  often  to 
cause  observable,  and  very  heavy,  shocks  ;  and,  often,  a 
succession  of  such  blows  is  heard,  the  intensity  of  which 
are  the  greater  as  the  pipe  is  heavier  and  larger,  and 
which  may  be  startling  and  even  very  dangerous.  It  is 
not  known  precisely  how  this  action  takes  place,  but  the 
author  has  suggested  the  following  as  a  possible  outline 
of  this  succession  of  phenomena :  * 

The  steam,  at  entrance,  passes  over,  or  comes  in 
contact  with,  the  surface  of  the  cold  water  standing  ir 
the  pipe.  Condensation  occurs,  at  first  very  slowl>, 
but  presently  more  quickly,  and  then  so  rapidly  that 
the  surface  is  broken,  and  condensation  is  completed 
with  such  suddenness  that  a  vacuum  is  produced.  The 
water  adjacent  to  this  vacuum  is  next  projected  vio- 
lently into  the  vacuous  space,  and,  filling  it,  strikes  on 
the  metal  surfaces,  and  with  a  blow  like  that  of  a  solid 
body,  the  liquid  being  as  incompressible  as  a  solid.  The 
intensity  of  the  resulting  pressure  is  the  greater  as  the 

*  Water-hammer  in  Steam-pipes ;  Trans.  Am.  Soc.  Mech.  Engrs.  ; 
vol.  iv.  p.  404. 


$o  STEAM  BOILER  EXPLOSIONS. 

distance  through  which  the  surface  attacked  can  yield 
is  the  less,  and  enormous  pressures  are  thus  attained, 
causing  the  leakage  of  joints,  and  even  the  straining, 
twisting  and  bursting  of  pipes.  In  some  cases,  the 
whole  of  an  extensive  line  or  system  of  pipes,  has  been 
observed  to  writhe  and  jump  about  to  such  extent  as  to 
cause  well-grounded  apprehensions. 

The  Author  once  had  occasion  to  test  the  strength  of 
pipes  which  had  been  thus  already  burst.  They  were  8 
inches  in  diameter  (20.32  cm.)  and  of  a  thickness  of  %&  inch 
(0.95  cm.)  and  had  been,  when  new,  subjected  to  a  press- 
ure of  about  20  atmospheres  (300  Ibs.  per  square  inch). 
When  tested  by  the  Author  in  their  injured  condition, 
they  bore  from  one-third  more  to  nearly  four  times  as 
high  pressures,  before  the  cracks  which  had  been  pro- 
duced were  extended.  It  is,  perhaps,  not  absolutely 
certain  that  some  of  these  pieces  of  pipe  may  not  have 
been  cracked  at  lower  pressures  than  the  above ;  but  it 
is  hardly  probable.  It  seems  to  the  Author  very  certain 
that  the  pressures  attained  in  his  tests  were  approxi- 
mately those  due  to  the  water-hammer,  or  were  lower. 
The  steam-pressure  had  never  exceeded  about  four  at- 
mospheres (60  Ibs.  per  sq.  in). 

It  is  evident  that  it  is  not  safe,  in  such  cases,  to  cal- 
culate simply  on  a  safe  strength  based  on  the  proposed 
steam-pressures,  but  the  engineer  may  find  those  actually 
met  with  enormously  in  excess  of  boiler-pressure,  and  a 
"  factor- of- safety  "  of  20  may  prove  too  small,  it  being 
found  as  above,  that  the  water-hammer  may  produce 


EN  ERG  Y  S  TOR  ED  IN  HE  A  TED  ME  TAL.  6 1 

local  pressure  approaching,  if  not  exceeding,  70  atmos- 
pheres (1000  Ibs.  per  sq.  inch). 

These  facts,  now  well  ascertained  and  admitted,  lend 
strong  confirmation  to  the  Clark  and  Colburn  theory  of 
explosions. 

15.  Energy  Stored  in  Heated  Metal  is  vastly  less  in 
amount,  with  the  same  range  of  temperature,  than  in 
water.  The  specific  heat  of  iron  is  but  about  one-ninth 
that  of  water,  and  the  weight  of  metal  liable  to  become 
overheated  in  any  boiler  is  very  small.  If  the  whole 
crown-sheet  of  a  locomotive  boiler  were  to  be  heated  to 
a  full  red-heat,  it  would  only  store  about  as  much  heat, 
per  degree,  as  forty  pounds  (18  kgs.)  of  water,  or  not 
far  from  3000  thermal  units  (756  calories),  or  2,316,000 
foot-pounds  (33,000  kilog-m.,  nearly),  or  about  three- 
tenths  of  the  total  energy  of  the  fluids  concerned  in  an 
explosion.  It  would  be  sufficient,  however,  to  consider- 
ably increase  the  quantity  of  steam  present  in  the  steam- 
space  ;  and  this  increase,  if  suddenly  produced,  and  too 
quickly  for  the  prompt  action  of  the  safety-valve,  might 
evidently  precipitate  an  explosion,  which  would  be 
measured  in  its  effects  by  the  total  energy  present. 

It  thus  becomes  at  once  obvious  that  the  danger  from 
the  presence  of  this  stock  of  excess  energy  is  deter- 
mined not  only  by  the  weight  of  metal  heated  and  its 
temperature,  but  even  more  by  the  rate  at  which  that 
surplus  heat  is  communicated  to  the  water  that  may  be 
brought  in  contact  with  it,  by  pumping  in  feed-water, 
or  by  any  cause  producing  violent  ebullition.  It  is 
probable  that  this  cause  has  sometimes  operated  to  pro- 


62  STEAM  BOILER  EXPLOSION'S. 

duce  explosions  ;  but  oftener,  that  the  loss  of  strength 
produced  by  overheating  is  the  more  serious  source  of 
danger.  It  is  also  evident  that  the  first  is  the  more 
dangerous,  as  the  pressures  are  lower,  the  second  with 
high  pressures. 

As     illustrating    a    calculation     in     detail,     assume 

(2.4  square  metres)  of  crown.sheet    or   boiler   shell 
(     25  square  feet     ) 


overheated  degrees  ^'    }     the    metal 

in  thickness  andits  t0tal 

kll°gs-    ?      Then    the    product    Of  Weight   into 
C  375  pounds.  } 

range   of  temperature,  into  specific   heat  (o.  Ill)  is   the 
measure  of  the  heat-energy  stored. 


375X1000X0.111=41,667  B.  T.  U.,  nearly; 
I7OX    556X0.111  =  10,502  calories         " 

and  in  mechanical  units, 

41,667X772     =32,167,924  foot-pounds,  nearly; 
10,502X423.55=4,448,122  kilog-metres,  nearly, 

which  is  fifteen  or  twenty  times  the  energy  stored  in  the 
steam  in  a  locomotive  boiler  in  its  normal  condition,  and 
about  one-half  as  much  as  ordinarily  exists  in  water  and 
steam  together.  It  is  evident  that  the  limit  to  the  destruc- 
tiveness  of  explosions  so  caused  is  the  rate  of  transfer  of 
this  energy  to  the  water  thrown  over  the  hot  plate, 


THE   STRENGTH  OF  HEATED   METAL.  63 

and  the  promptness  with  which  the  steam  made  can  be 
liberated  at  the  safety-valve.  A  sudden  dash  of  water 
or  spray  over  the  whole  of  such  a  surface  might  be 
expected  to  even  produce  a  "  fulminating  explosion." 
Fortunately,  as  experience  has  shown,  so  sudden  a 
transfer,  or  so  complete  a  development  of  energy,  rarely, 
perhaps  never,  takes  place. 

16.  The  Strength  of  Heated  Metal  is  known  usually 
to  decrease  gradually  with  rise  in  temperature,  until,  as 
the  welding  or  the  melting  point,  as  the  case  may  be,  is 
approached,  it  becomes  incapable  of  sustaining   loads. 
Both  iron  and.  steel,  however,  lose  much  of  their  tena- 
city at  a  bright  red  heat;  at  which  point  they  have 
less  than  one-fourth  that  of  ordinary  temperature.     A 
steam-boiler  in  which  any  part  of  the  furnace  is  left  un- 
protected by  the  falling  of    the    water-level,    is   very 
likely  to  yield  to  the  pressure,  and   an   explosion   may 
result  from  simple  weakness.     At  temperatures  well  be- 
low the  red-heat,  this  will  not  happen. 

17.  Low  Water,    in  consequence   of    the  obvious 
dangers    which    attend    it    and     the     not    infrequent 
narrow    escapes   which    have   been    known,    has    often 
been,  by   experienced  engineers,  considered  to   be   the 
most  common,  even  the  almost  invariable,  cause  of  ex- 
plosions.    This  view  is  now  refuted  by  statistics  and  a 
more  extended  observation  and  experience  ;    but  it  re- 
mains   one    of  the    undeniable    sources   of  danger  and 
causes  of  accident. 

Its  origin  is  usually  in  some  accidental  interruption  of 
the  supply  of  feed-water;   less  often  an  unobserved  leak 


6  4  STEAM  BOILER   EXPLOSIONS. 

or  accelerated  production  of  steam.  Whatever  the 
cause,  the  result  is  the  uncovering  of  those  portions  of 
the  heating-surface  which  are  highest,  and  their  ex- 
posure, unprotected  by  any  efficient  cooling  agency,  to 
the  heat  of  the  gases  passing  through  the  flue  at  that 
point  Should  it  be  the  case  of  a  locomotive,  or  other 
boiler,  having  the  crown-sheet  of  its  fire-box  so  placed 
as  to  be  first  exposed,  when  the  water-level  falls,  the 
iron  may  become  heated  to  a  full  red-heat;  if  the 
highest  surfaces  are  those  of  tubes,  through  which 
gases  approximating  the  chimney  in  temperature  are 
passing,  the  heat  and  the  danger  are  less.  In  either 
case,  danger  is  incurred  only  when  the  temperature  be- 
comes such  as  to  soften  the  iron,  or  when  the  return  of 
the  water  with  considerable  rapidity  gives  rise  to  the 
production  of  steam  too  rapidly  to  be  relieved  by  the 
safety-valve  or  other  outlet.  Such  explosions  probably 
very  seldom  actually  occur,  even  when  all  conditions 
seem  favorable.  Every  boiler-making  establishment  is 
continually  collecting  illustrations  of  the  fact  that  a 
sheet  may  be  overheated,  and  may  even  alter  its  form 
seriously,  when  overheated,  without  completely  yielding 
to  pressure,  and  the  Author  has  taken  part  in  many  at- 
tempts to  experimentally  produce  explosions  by  pump- 
ing feed-water  into  red-hot  boilers,  and  has  but  once 
seen  a  successful  experiment  The  same  operation  in 
the  regular  working  of  boilers  has  been  often  performed 
by  ignorant  or  reckless  attendants  without  other  dis- 
aster than  injury  to  the  boiler;  but  it  has  unquestion- 
ably, on  other  occasions,  caused  terrible  loss  of  life  and 


LOW    WATER.  65 

property.  The  raising  of  a  safety-valve  on  a  boiler  in 
which  the  water  is  low,  by  producing  a  greater  violence 
of  ebullition  in  the  water  on  all  sides  the  overheated 
part,  may  throw  a  flood  of  solid  water  or  of  spray  over 
it ;  and  it  is  possible  that  this  has  been  a  cause  of  many 
explosions.  The  Author  has  seen  but  a  single  explosion 
produced  in  this  way,  although  he  has  often  attempted 
to  produce  such  a  result.  In  three  experiments  on  a 
certain  cylindrical  boiler,  empty,  and  heated  to  the  red- 
heat,  the  result  of  rapidly  pumping  in  a  large  quantity 
of  water  was,  in  the  first,  the  production  of  a  vacuum, 
in  the  second  an  excess  of  pressure  safely  and  easily 
relieved  by  the  safety-valve ;  and  in  the  third  case  a 
violent  explosion  of  the  boiler  and  the  complete  de- 
struction of  the  brick  setting.*  The  boiler  experi- 
mented upon  was  set  in  brickwork  in  the  usual  man- 
ner. In  each  experiment,  the  boiler  was  filled  with 
water,  a  fire  started,  and,  when  the  fire  was  in  good 
order  and  the  steam  at  the  right  point,  all  water  was 
blown  out ;  the  boiler  was  allowed  to  become  heated  to 
the  desired  temperature,  as  indicated  by  a  pyrometer 
inserted  within  it,  and,  at  the  proper  moment,  the  feed- 
water  was  introduced  by  a  force-pump.  At  each  occa- 
sion, on  the  introduction  of  the  water,  the  steam-press- 
ure rose  suddenly,  the  safety-valve  opened,  and,  the 
water  still  continuing  to  enter,  the  boiler-pressure 
dropped  almost  as  rapidly  as  it  had  risen,  and  the  boiler 
cooled  down  on  each  occasion  (except  the  last)  without 

*Sci.  Am.,  Sept.  1875. 


66  STEAM  BOILER  EXPLOSIONS. 

apparent  injury,  and  without  having  even  started  a 
seam,  although  the  metal  had  been  red  hot. 

The  last  experiment  resulted  in  the  explosion  of  the 
boiler  and  the  destruction  of  its  setting,  and  interrupted 
the  work.  The  succession  of  phenomena  was  in  this 
case  precisely  as  already  described ;  but  the  tempera- 
ture of  the  boiler  was  on  this  occasion  higher,  probably 
a  bright  red  on  the  bottom,  and  the  pressure  of  steam 
was  about  60  Ibs.  before  the  explosion  occurred.  It  had 
fallen  somewhat  from  the  maximum,  attained  the  mo- 
ment before.  A  committee  of  the  Franklin  Institute, 
conducting  similar  experiments, t  had  the  same  exper- 
ience, the  pressure  "  rising  from  one  to  twelve  atmos- 
pheres within  ten  minutes,"  after  starting  the  pump. 
The  most  rapid  vaporization  occurs,  as  is  well  known,  at 
a  comparatively  low  temperature  of  metal ;  at  high 
temperature  the  spheroidal  condition  is  produced,  and 
no  contact  exists  between  metal  and  liquid. 

Mr.  C.  A.  Davis,  President  of  the  New  York  and  Bos- 
ton Steamboat  Co.,  in  a  letter  addressed,  Dec.  7,  1831, 
to  the  Collector  of  the  Port  of  New  York,  and  con- 
cerning inquiries  of  the  U.  S.  Treasury  Department, 
wrote :  * 

"  I  have  noted  that  by  far  the  greater  number  of  ac- 
cidents by  explosion  and  collapsing  of  boilers  and  flues, 
I  might  say  seven-tenths,  have  occurred  either  while  the 
boat  was  at  rest,  or  immediately  on  starting,  particu- 

f  Journal  Franklin  Inst. ,  1837,  vol.  17. 
*  Report  of  Steam  Boilers,  H.  R.,  1832. 


LOW    WATER,  67 

larly  after  temporary  stoppages  to  take  in  or  land  pas- 
sengers. These  accidents  may  occur  from  directly 
opposite  causes,  either  by  not  letting  off  enough  steam,  or 
by  letting  off  too  much;  the  latter  is  by  far  the  most  de- 
structive." 

The  idea  of  this  writer  was  that  the  "  letting  off  of 
too  much  "  steam,  by  producing  low  water,  was  the  most 
frequent  cause  of  explosions,  an  idea  which  has  never 
since  been  lost  sight  of. 

The  chief  engineer  of  the  Manchester  (G.  B.)  Steam 
Boiler  Association,  in  1 866-89  repeatedly  injected  water 
into  overheated  steam-boilers,  but  never  succeeded  in 
producing  an  explosion.*  Yet,  as  has  been  seen,  such 
explosions  may  occur. 

A  writer  in  the  Journal  of  the  Franklin  Institute,!  a 
half  century  or  more  ago,  asserted  that  "  the  most 
dreadful  accidents  from  explosions  which  have  taken 
place,  have  occurred  from  low-pressure  boilers."  It 
was,  as  he  states,  "  a  fact  that  more  persons  had  been 
killed  by  low  than  by  high-pressure  boilers."  Nearly  all 
writers  of  that  time  attributed  violent  explosions  to  low 
wates,  and  some  likened  the  phenomenon  to  that  ob- 
served when  the  blacksmith  strikes  with  a  moist  ham- 
mer on  hot  iron. 

Thus,  if  the  boiler  is  strong,  and  built  of  good  iron, 
and  not  too  much  overheated,  or  if  the  feed-water  is  in- 
troduced slowly  enough,  it  is  possible  that  it  may  not 

*  Mechanics'  Magazine,  May,    1867  ;   also  Chief  Eng'r's    Report. 
Dec.  10,  1889. 
f  Vol.  3  ;  pp.  335,  418,  420. 


68  STEAM  BOILER  EXPLOSIONS. 

be  exploded  ;  but  with  weaker  iron,  a  higher  tempera- 
ture,  or  a  more  rapid  development  of  steam,  explosion 
may  occur.  Or,  if  the  metal  be  seriously  weakened  by 
the  heat,  the  boiler  may  give  way  at  the  ordinary  or  a 
lower  pressure,  v»hich  result  may  also  be  precipitated  by 
the  strains  due  to  irregular  changes  of  dimension  ac- 
companying rapid  and  great  changes  of  temperature. 
Explosions  due  to  low  water,  when  there  is  a  consid- 
erable mass  of  water  below  the  level  of  the  overheated 
metal,  are  sometimes  fearfully  violent,  a  boiler  com- 
pletely emptied  of  water,  and  only  exploded  by  the 
volume  of  steam  contained  within  it,  is  far  less  danger- 
ous. Low  water  and  red-hot  metal  in  a  locomotive  or 
other  fire-box  boiler,  are,  for  this  reason,  far  more  dan- 
gerous than  in  a  plain  cylindrical  boiler;  as  was  indica- 
ted by  the  experiments  conducted  by  the  Author,  the 
latter  must  be  entirely  deprived  of  water  before  this 
dangerous  condition  can  arise.  In  the  course  of  the  nu- 
merous experiments  already  alluded  to,  many  attempts 
were  made  to  overheat  the  latter  class  of  boiler,  but  none 
were  successful  until  the  water  was  entirely  expelled. 
Experiments,  with  apparatus  devised  for  the  purpose  of 
keeping  the  steam  moist  under  all  circumstances,  indi- 
cate that  it  is  difficult,  if  not  impossible,  to  overheat 
even  an  uncovered  fire-box  crown -sheet,  if  the  steam 
be  kept  moist,  and  that  such  steam  is  very  nearly  as 
good  a  cooling  medium,  in  such  cases,  as  the  water 
itself. 


LOW    WATER.  69 

Figure  5  *  represents  a  boiler  exploded  by  the  intro- 
duction of  water,  after  it  had  been  emptied  by  care- 
lessly leaving  open  the  blow-cock.  This  boiler  was 


FIG.  5.— BOILER  EXPLODED  ;  CAUSE,  Low  WATER. 

about  five  years  old,  and  the  explosion,  as  is  usual  in 
such  cases,  was  not  violent,  the  small  amount  of  water 
entering  and  the  weakness  of  the  sheet  conspiring  to 
prevent  the  production  of  very  high  pressure,  or  the 
storage  of  much  energy.  The  whole  of  the  lower  part 
of  the  shell  of  the  boiler  was  found,  on  subsequent  ex- 
amination, to  have  been  greatly  overheated.  One  man 
was  killed  by  the  falling  of  the  setting  upon  him ;  no 
other  damage  was  done. 

Figure  6  shows  the  effect  of  a  similar  operation  on  a 
water-tube  boiler.     The  feed-water  was  cut  off,  and  not 

*  The  Locomotive  ;  Sept.  1886  ;  p.  129. 


7o  STEAM  BOILER   EXPLOSIONS. 

noticed  until  the  water-level  became  so  low  that  the 
boiler  was  nearly  empty  and  the  tubes  were  overheated. 
One  of  the  tubes  burst,  and  the  damage  was  speedily 


FIG.  6.— TUBE  BURST  ;  Low  WATER. 

repaired  at  a  cost  of  $15,  and  the  works  were  running 
the  next  day.* 

That  low  water  and  the  consequent  overheating  of 
the  boiler  does  not  necessarily  produce  disaster,  even 
when  the  water  is  again  supplied  before  cooling  off, 
was  shown  as  early  as  181 1,  by  the  experience  of  Cap- 
tain E.  S.  Bunker  of  the  Messrs.  Stevens's  steamboat 
"  Hope,"  then  plying  between  New  York  and  Albany. 
During  one  of  the  regular  passages,  he  discovered  that 
the  water  had  been  allowed,  by  an  intoxicated  fireman, 
to  completely  leave  both  the  boilers.  He  at  once 
started  the  pump  and,  filling  up  the  boilers,  proceeded 
on  his  way,  no  other  sign  of  danger  presenting  itself 
than  "  a  crackling  in  the  boiler  as  the  water  met  the 
hot  iron,  the  sound  of  which  was  like  that  often  heard 
in  a  blacksmith's  shop  when  water  is  thrown  on  a  piece 
of  hot  iron."  t  A  year  later,  Captain  Bunker  repeated 
this  experience,  at  Philadelphia,  on  the  "  Phoenix," 

*G.  H.  Babcock. 

f  Doc.  No.  21,  H.  R.,  25th  Congress,  3rd  Session,  1838,  p.  103. 


\_Toface  page  70.] 


FIG.  6A.— AN  UNEXPLAINED  FAILURE. 


LOW  WATER.  71 

where  the  boilers  where  of  the  same  number  and  size 
as  those  of  the  "Hope."  * 

Defective  circulation  may  cause  the  formation  of  a 
volume  of  steam  in  contact  with  a  submerged  portion 
of  the  heating  surface.  The  Author,  when  in  charge  of 
naval  engines  during  the  civil  war,  1861-5,  found  it  pos- 
sible, on  frequent  occasions  to  draw  a  considerable 
volume  of  practically  dry  steam  from  the  water-space 
between  the  upper  parts  of  two  adjacent  furnaces  at  a 
point  two  or  three  feet  below  the  surface-water  level. 
After  drawing  off  steam  for  a  few  seconds,  through  a 
cock  provided  to  supply  hot  water  for  the  engine  and 
fire-rooms,  water  would  follow  as  in  the  normal  condi- 
tion of  the  boiler.  This  condition  often  occurs  in  some 
forms  of  boiler  and  has  been  occasionally  observed  by 
every  experienced  engineer.  It  would  not  seem  im- 
possible, therefore,  that  steam  might  be  sometimes  thus 
encaged  in  contact  with  the  furnace,  and  thus  cause 
overheating  of  the  adjacent  metal.  Many  such  in- 
stances have  been  related,  but  they  have  been  com- 
monly regarded  by  the  inexperienced  as  somewhat 
apochryphal.t 

In  order  that  the  danger  of  overheating  the  crown- 
sheet  of  the  locomotive  type  of  boiler  may  be  lessened, 
it  is  very  usual  to  set  it  lower  at  the  fire-box  end,  when 
employed  as  a  stationary  boiler,  so  as  to  give  a  greater 
depth  of  water  over  the  crown-sheet  than  over  the 

*Ibid. 

f  See  London  Engineer,  Dec.  7,  1860,  pp.  371,  403. 


7 2  STEAM  BOILER   EXPLOSIONS. 

tubes  at  the  rear.  The  plan  of  giving  greatest  depth  of 
water,  when  possible,  at  that  end  of  the  boiler  at  which 
the  heating-surfaces  near  the  water-surface  are  hottest,  is 
always  a  good  one. 

Mr.  Fletcher  concluded  from  his  experiments  that 
low  water  is  only  a  cause  of  danger  by  weakening  the 
overheated  plates.  He  says  :* 

"  These  experiments,  it  is  thought,  may  be  accepted 
as  conclusive  that  the  idea  of  an  explosion  arising  from 
the  instantaneous  generation  of  a  large  amount  of  steam 
through  the  injection  of  water  on  hot  plates  is  a  fallacy." 

The  conclusion  of  the  Author,  in  view  of  the  experi- 
ments of  the  committee  of  the  Franklin  Institute  and  of 
his  own  personal  experience  in  the  actual  production  of 
explosions  by  this  very  process,  as  elsewhere  described, 
does  not  accord  with  the  above ;  but  it  is  sufficiently 
well  established  that  low  water  may  frequently  occur 
and  feed-water  may  be  thrown  upon  the  overheated 
plate  without  necessarily  causing  explosion.  Danger 
does,  however,  certainly  always  arise,  and  such  explo- 
sions have  most  certainly  occurred — possibly  many  in 
the  aggregate. 

Low-water  is  certainly  very  rarely,  perhaps  almost 
never,  the  cause  of  explosion  of  other  than  fire-box 
boilers ;  in  these,  however,  the  danger  of  overheating 
the  crown-sheet  of  the  furnace,  if  the  supply  of  water 
fails,  is  very  great,  and,  in  such  cases,  explosion  is  always 
to  be  feared.  The  most  disastrous  explosions  are  usually 


*  London  Engineer,  March  15,  1867,  p.  228. 


SEDIMEN  T  A  XD  I  NCR  US  TA  TION.  7  3 

those,  however,  in  which  the  supply  of  water  is  most 
ample. 

18.  Sediment  and  Incrustation  sometimes  produce 
the  effect  of  low- water  in  boilers,  even  where  the  surfaces 
affected  are  far  below  the  surface  of  the  water.  Every 
increase  of  resistance  to  the  passage  of  heat  through  the 
metal  and  the  encrusting  layer  of  sediment  or  scale 
causes  an  increase  of  temperature  in  the  metal  adjacent 
to  the  flame  or  hot  gases,  until,  finally,  the  incrustation 
attaining  a  certain  thickness,  the  iron  or  steel  of  the 
boiler  becomes  very  nearly  as  hot  as  the  gases  heating 
it.  Should  this  action  continue  until  a  red-heat,  or  a 
white-heat,  even,  as  sometimes  actually  occurs,  is 
reached,  the  resistance  becomes  so  greatly  reduced  that 
the  sheet  yields,  and  either  assumes  the  form  of  a 
"  pocket,"  or  depression,  as  often  happens  with  good 
iron  and  with  steel ;  or  it  cracks,  or  it  even  opens  suffi- 
ciently to  cause  an  explosion.  "  Pockets  "  often  form 
gradually,  increasing  in  depth  day  by  day,  until  they 
are  discovered,  cut  out,  and  a  patch  or  a  new  sheet  put 
in,  or  until  rupture  takes  place.  In  such  cases,  the 
incrustation  keeps  the  place  covered  while  permitting 
just  water  enough  to  pass  in  to  cause  the  extension  of 
the  defect. 

In  some  cases,  the  process  is  a  different  and  a  more 
disastrous  one.  The  scale  covers  an  extended  area, 
permitting  it  to  attain  a  high  temperature.  After  a  time 
a  crack  is  formed  in  the  scale  by  the  unequal  expansion 
of  the  two  substances  and  the  inextensibility  of  the 
incrustation ;  and  water  entering  through  this  crack  is 


74 


STEAM  BOILER  EXPLOSIONS. 


exploded  into  steam,  ripping  off  a  wide  area  of  incrusta- 
tion previously  covering  the  overheated  sheet,  and  giv- 
ing rise  instantly,  probably,  to  an  explosion  which 
drives  the  sheet  down  into  the  fire,  and  may  also  rend 
the  boiler  into  pieces,  destroying  life  and  property  on 
every  side.  Such  an  explosion  usually  takes  place  with 
the  boiler  full  of  water  and  its  stored  energy  a  maximum, 
and  the  result  is  correspondingly  disastrous. 

Certain  greasy  incrustations,  and  some  flowery  forms 
of  mineral  or  vegetable  deposits,  have  been  found 
peculiarly  dangerous,  as,  in  even  exceedingly  thin 
layers,  they  are  such  perfect  non-conductors  as  to 
speedily  cause  overheating,  strains,  cracks,  leakage,  and, 
often,  explosion.  M.  Arago  mentions  a  case  in  which 
rupture  occurred  in  consequence  of  the  presence  of  a  rag 
lying  on  the  bottom  of  a  boiler.* 

The  effect  of  incrustation  in  causing  the  overheating 
of  the  fire-surfaces,  the  formation  of  a  "  pocket,"  and 
final  rupture,  is  well  shown  in  the  three  illustrations 
which  follow. 

When  the  water  is  fully  up  to  the  safe  level,  as  at  the 
right  in  the  first  of  the  three  figures,  the  heat  received 
from  the  furnace  gases  is  promptly  carried  away  by  the 
water  and  the  sheet  is  kept  cool.  When  the  water  falls 
below  that  level,  or  is  prevented,  by  incrustation,  from 
touching  the  metal,  as  in  the  left-hand  illustration,  the 
sheet  becomes  red-hot,  soft,  and  weak,  and  yields  as 
shown.  When  this  goes  on  to  a  sufficient  extent,  as  on 

*  Report  of  the  Committee  of  the  Franklin  Institute. 


SEDIMENT  AND  INCRUSTATION. 


75 


FIG.  7. — OVERHEATING  THE  SHEET. 


a  horizontal  surface,  figure  8,  a  pocket  is  produced.  The 
illustration    represents  a  sheet  removed  from  the  shell 


FIG.  8.— A  "  POCKET.' 


of  an  externally  fired  boiler,  thus  injured. 

Finally,  when  the  defect  is  not  observed  and  the 
injured  sheet  removed,  the  metal  may  finally  give  way 
entirely,  permitting  the  steam  and  water  to  issue,  as  in 
the  last  illustration  of  this  series,  in  which  the  last  step 


FIG.  9. — RUPTURED  POCKET. 


76 


STEAM  BOILER  EXPLOSIONS. 


in  the  process  is  well  represented.  Where  the  area  thus 
affected  is  considerable,  the  result  may  be  a  general 
breaking  up  of  that  portion  of  the  shell,  as  in  the  next 
figure,  and  an  explosion  may  prove  to  be  the  final  step 


FIG.  io.— SHELL  RUPTURED. 


in  the   chain  of  phenomena  described.     In  other  cases 
where,  as  in  the  next  sketch,  a  line  of  weakness  may  be 


...A... 


FIG.  ii. — EXTENDED  RUPTURE. 


the  result  of  other  causes ;  a  large  section  of  the  boiler 
may  be  broken  out,  as  at  A  D,  Figure  1 1. 

The  deposition  of  sediment  and  of  scale  takes  place 
in  the  boiler.  Not  only  in  the  boiler,  but  also  with 
some  kinds  of  water  in  the  feed-pipe,  as  is  illustrated  in 


SEDIMENT  AND  INCRUSTATION.  77 


FIG.  12. — INCRUSTATION  IN  FEED-PIPE. 

the  accompanying  engraving,  which  is  made  from  an 
actual  case  in  which  the  pipe  was  so  nearly  filled  as  to 
become  quite  incapable  of  performing  its  office.  A  cur- 
rent has  apparently  no  effect,  in  many  such  cases,  in 
preventing  the  deposition  of  scale.  The  Author  has 
known  hard  scale  to  form  in  the  cones  of  a  Giffard  in- 
jecter  under  his  charge,  where  the  steam  was  moving 
with  enormous  velocity,  and  loudly  whistling  as  it 
passed. 

Instances  are  well  known  of  the  explosion,  with  fatal 
effect  of  open  vessels,  in  consequence  of  the  action  above 
described.  Mr.  G.  Gurney,  in  1831,  gave  an  account  of 
such  an  explosion  of  the  water  in  an  open  cauldron  at 
Meux's  brewery,  by  which  one  person  was  killed  and 
several  others  injured.*  It  was  found  that  the  bottom 
had  become  encrusted  with  sediment,  and  the  sudden 
rupture  of  the  film,  permitting  contact  of  the  water 
above  with  the  overheated  metal  below,  caused  such  a 
sudden  and  violent  production  of  steam  that  it  actually 

*  Report  on  Steam  Carriages  ;  Doc.  101,  22nd  Congress,  1st  Session, 
P-  31- 


7 8  STEAM  BOILER  EXPLOSIONS. 

ruptured  the  vessel.  The  process  of  which  this  is  an 
illustration  is  precisely  analogous  to  suddenly  throwing 
feed-water  into  an  overheated  boiler. 

19.  Energy  Stored  in  Superheated  Water  has  been 
sometimes  considered  a  source  of  danger  to  steam  boil- 
ers and  a  probable  cause  of  explosions.  The  magni- 
tude of  this  stock  of  energy  is  not  likely  to  differ 
greatly  from  that  of  water  at  the  same  temperature  un- 
der the  pressure  due  that  temperature,  and,  for  present 
purposes,  it  may  be  taken  as  approximately  unity.  The 
quantity  of  heat  so  stored  is,  therefore,  measured  very 
nearly  by  the  product  of  the  weight  of  water  so  over- 
heated, the  mean  range  of  superheating,  and  the  specific 
heat  here  taken  as  unity.  It  is  not  known  how  large  a 
part  of  the  water  in  any  boiler  can  be  superheated,  or 
the  extent  to  which  this  action  can  occur.  It  is  to  be 
doubted,  however,  whether  it  can  take  place  at  all  in 
steam-boilers. 

To  secure  this  condition  the  experiment  of  M.M. 
Donny,  Dufour,  and  others  show  that  the  larger  the 
mass  of  water,  the  less  the  degree  of  superheating  attain- 
able; the  more  impure  the  water,  or  the  greater  the 
departure  from  the  condition  of  distilled  water,  and  the 
larger  the  proportion  of  air  or  sediment  mechanically 
suspended,  the  more  difficult  is  it  to  attain  any  consid- 
erable superheating. 

As  early  as  1812*  Gay-Lussac  observed  a  retarda- 

*  Ann.  de  Chemie  et  de  Physique,  Ixxxii. 


ENERGY  STORED  IN  SUPERHEATED    WATER.     79 

tion  of  ebullition  in  glass  vessels ;  thirty  years  later,* 
M.  Marcet  found  that  water,  deprived  of  air,  can  be  raised 
several  degrees  above  its  normal  boiling  point,  while 
Donny,t  Dufour,f  Magnus,  §  and  Grove  ft  all  succeeded 
in  developing  this  phenomenon  more  or  less  remark- 
ably. Donny,  sealing  up  water,  deprived  of  air,  in 
glass  tubes,  succeeded  in  raising  the  boiling  point  to 
138°  C.  (280°  F.),  at  which  temperature  vaporization 
finally  occurred  explosively.  Dufour,  by  floating  glo- 
bules of  pure  water  in  a  mixture  of  oils  of  density 
equal  to  that  of  the  water,  succeeded  with  very  minute 
globules,  in  raising  the  boiling  point  to  173°  C. 
(347°  F.)  at  \vhich  temperature  the  normal  tension  of 
its  steam  is  1 1 5  pounds  per  square  inch  (nearly  8  at- 
mospheres) by  gauge.  In  such  cases,  the  touch  of  any 
solid,  or  of  bubbles  of  gas,  would  produce  explosive 
evaporation.  Solutions  always  boil  at  temperatures 
somewhat  exceeding  the  boiling  point  of  water,  but 
usually  quietly  and  steadily.  In  all  these  cases,  the 
rise  in  temperature  seems  to  have  been  greater  the 
smaller  the  mass  of  water  experimented  with. 

In  all  ordinary  cases  of  steam-boiler  operation,  the 
mass  of  water  is  simply  enormous  as  compared  with  the 
quantities  employed  in  the  above-described  laboratory 
experiments;  the  water  is  almost  never  pure,  and 
probably  as  invariably  contains  more  or  less  air.  It 

*  Bibl.  Univ.,  xxxviii. 

f  Ann.  de  Chemie  et  de  Physique,  3ve,  Seriet.  xvi. 

JBibl.  Univ.  Nov.  1861,  t.  xii. 

§ Poggendorff 's  Ann.,  t.  cxiv.     ff  Cosmos,  1863. 


8o  STEAM  BOILER  EXPLOSIONS. 

would  seem  very  unlikely  that  such  superheating  could 
ever  occur  in  practice.  There  is,  however,  some  evi- 
dence indicating  that  it  may. 

Mr.  Wm.  Radley  *  reports  experimenting  with  small 
laboratory  boilers  of  the  plain  cylindrical  form,  and 
continuing  slowly  heating  them  many  hours,  finally  at- 
taining temperatures  exceeding  the  normal  by  15°  F. 
(8.3°  C.)  The  investigator  concludes: 

"  Here  we  have  conclusive  data  suggesting  certain 
rules  to  be  vigorously  adopted  by  all  connected  with 
steam-boilers  who  would  avoid  mysterious  explosions: 
First,  never  feed  one  or  more  boilers  with  surplus  water 
that  has  been  boiled  a  long  time  in  another  boiler,  but 
feed  each  separately.  Second,  when  boilers  working 
singly  or  fed  singly  are  accustomed,  under  high  pressure, 
to  be  worked  for  a  number  of  hours  consecutively,  day 
and  night,  they  should  be  completely  emptied  of  water 
at  least  once  every  week,  and  filled  with  fresh  water. 
Third,  in  the  winter  season  the  feed-water  of  the  boiler 
should  be  supplied  from  a  running  stream  or  well ;  thaw 
water  should  never  be  used  as  feed  for  a  boiler." 

"  Locomotive,  steamboat,  and  stationary  engine  boil- 
ers have  their  fires  frequently  banked  up  for  hours, 
without  feeding-water,  and  the  steam  fluttering  at  the 
safety-valve,  so  as  to  have  them  all  ready  for  starting  at 
at  a  moment.  This  is  a  dangerous  practice,  as  the  fore- 
going experiments  demonstrate.  While  so  standing, 
all  the  atmospheric  air  may  be  expelled  from  the  water, 

*  London  Mining  Journal,  June  28,  1856. 


ENERGY  STORED  IN  SUPERHEATED   WATER.     81 

and  it  may  thereby  attain  to  a  high  heat,  ready  to  gen- 
erate suddenly  a  great  steam- pressure  when  the  feed- 
pump is  set  in  motion.  This  is,  no  doubt,  the  cause  of 
the  explosion  of  many  steam-boilers  immediately  upon 
starting  the  engine,  even  when  the  gauge  indicates 
plenty  of  water.  The  remedy  for  such  explosions  must 
be  evident  to  e^ery  engineer — keep  the  feed-pump 
going,  however  small  may  be  the  feed  required." 

On  the  other  hand,  the  report  of  a  committee 
appointed  by  the  French  Academy  to  inquire  into  the 
superheated  water  theory  of  steam-boiler  explosions, 
indicates  at  least  the  difficulty  of  securing  such  condi- 
tions.* The  committee  constructed  suitable  apparatus, 
experimented  in  the  most  exhaustive  manner,  and 
investigated  several  explosions  claimed  by  the  advocates 
of  the  theory  to  have  been  due  to  this  cause.  They 
failed  to  superheat  water  under  any  conditions  which 
could  probably  occur  in  practice,  and  the  explosions 
investigated  were  shown  conclusively  to  have  resulted 
from  simple  deterioration  of  the  boilers,  or  from  care- 
lessness. 

It  is  unquestionably  the  fact  that  explosions  due  to 
this  cause  are  at  least  exceedingly  rare,  although  it  is 
not  at  all  certain  that  they  may  not  now  and  then  take 
place.  The  ocean  is  constantly  being  traversed  by 
thousands  of  steamers  having  surface  condensers  and 
boilers  in  which  the  water  is  used  over  and  over  again, 
and  in  which  is  every  condition  seemingly  favorable  to 


*Annales  de  Mines,  1886. 


82  STEAM  BOILER  EXPLOSIONS. 

such  superheating  of  the  water ;  but  no  one  known 
instance  has  yet  occurred  of  the  production  of  this  phe- 
nomenon, there  or  elsewhere,  on  a  large  scale,  where 
boilers  are  in  regular  operation. 

M.  Donny,  who  first  suggested  the  possibility  of 
this  action  as  a  cause  of  boiler-explosions,  has  had 
many  followers.  M.  Dufour,*  who  doubts  if  such  ex- 
plosions are  possible  in  the  ordinary  working  of  the 
boiler,  points  out  the  fact,  however,  that  boilers  which 
are  quietly  cooling  down,  after  the  working  hours  are 
over,  are  peculiarly  well  situated  for  the  development  of 
this  form  of  stored  energy.  He  points  out  the  known 
fact  that  many  explosions  have  taken  place  under  such 
conditions,  the  pressure  having  fallen  below  the  work- 
ing-pressure. M.  Gaudryt  makes  the  same  observation. 
Such  cases  are  supposed  to  be  instances  of  "  retarded 
ebullition,"  with  decrease  of  pressure  and  superheating 
of  the  water.  Many  circumstances  unquestionably  tend 
to  strengthen  this  view. 

So  tremendous  are  the  effects  of  many  explosions 
that  M.  Andrand  has  expressed  the  belief  that  a  true 
explosion  must  be  preceded  by  pressure  approaching  or 
exceeding  200  atmospheres,!  an  intensity  of  pressure, 
however,  which  no  boiler  could  approximate.  Mr.  Hall, 
also,  thinks  that  the  shattering  effect  sometimes  wit- 
nessed, resulting  in  the  shattering  of  a  boiler  into  small 

*  Sur  1' Ebullition  de  1'Eau,  et  sur  une  cause  probable  d'  Explosion  des 
Chandlers  a  vapeur,  p.  29. 

f  Traite  des  Machines  a  Vapeur. 
jComptes  Rendes,  May  1855,  p.  1062. 


ENERGY  STORED  IN  SUPERHEATED   WATER.      83 

pieces,  must  be  the  effect  of  a  sudden  and  enormous 
force  partaking  of  the  nature  of  a  blow,*  and  cites  cases, 
such  as  are  now  known  to  be  common,  of  an  explosion 
taking  place  on  starting  an  engine  after  the  boiler  has 
been  at  rest  and  making  no  steam  for  a  considerable 
time.  M.  Arago  cites  a  number  of  similar  instances,t 
and  Robinson  a  number  in  still  greater  detail.}:  Boilers, 
after  quietly  "  simmering  "  all  night,  exploded  at  the 
opening  of  the  throttle-valve  or  the  safety-valve  in  the 
morning.  The  locomotive  "Wauregan,"  which  exploded 
within  sight  and  hearing  of  the  Author,  at  Providence, 
R.  I.,  in  February,  1856,  is  mentioned  by  Colburn  as  such 
a  case.  The  engine  had  been  quietly  standing  in  the  en- 
gine house  two  hours,  the  engineer  and  fireman  engaged 
cleaning  and  packing,  preparatory  to  starting  out.  The 
explosion  was  without  warning  and  very  violent,  strip- 
ping off  the  shell  and  throwing  it  up  through  the  roof, 
and  killing  the  engineer,  who  was  standing  beside  his 
engine. 

Mr.  Robinson^  thinks  the  usual  cause  of  such  explo- 
sions is  the  overheating  of  the  water,  the  phenomenon 
being  in  its  effects  very  like  the  "  water-hammer "  in 
steam-pipes,  producing  shocks  which  the  Author  has 
shown  to  give  rise  to  instantaneous  pressures  exceeding 
the  working-pressures  ten  or  twenty  times  ;  the  action, 

*  Civil  Engineers'  Journal,   1856,  p.   133  ;     Dingler's  Journal,    1856, 
p.  12. 

f  Annuaire,  1830. 

JSt.  Boiler  Explos.,  p.  62. 

§  Ibid,  p.  66. 


84  STEAM  BOILER  EXPLOSIONS. 

however,  seems  rather  to  be  that  "  boiling  with  bumping  " 
familiar  to  chemists  handling  sulphuric  acid  in  consider- 
able quantities.  Instances  have  been  known  in  which 
this  bumping  has  burst  pipes  or  severely  shaken  boilers 
and  setting  without  producing  explosion. 

The  de-aeration  of  water,  and  the  subsequent  super- 
heating of  the  liquid,  to  which  some  explosions  have 
been  attributed,  are  phenomena  which  have  been  often 
investigated.  Mr.  A.  Guthrie,  formerly  U.  S.  Super- 
vising Inspector  General  of  Steam-vessels,  states  that  he 
made  many  such  experiments,  as  follows:  * 

"  (i.)  In  my  experiments,  I  first  procured  a  sample 
of  water  from  the  boiler  of  an  ordinary  condensing  en- 
gine; here,  of  course,  in  addition  to  being  subjected  to 
long-continued  boiling,  it  had  passed  through  the  va- 
cuum. 

(2.)  I  procured  a  sample  from  the  ordinary  high 
pressure  non-condensing  engine  boiler,  which  before 
entering  the  boiler  had  passed  the  heater  at  210°. 

(3.)  I  procured  some  clean  snow  and  dissolved  it 
under  oil,  so  that  there  was  no  contact  with  the  air. 

(4.)  I  froze  some  water  in  a  long,  upright  tube,  using 
only  the  lower  end  of  the  ice  when  removed  from  the 
tube,  and  dissolved  under  oil. 

(5.)  I  placed  a  bottle  of  water  under  a  powerful  va- 
cuum pump  worked  by  steam,  for  two  hours ;  agitating 
the  water  from  time  to  time  to  displace  any  air  that 
might  possibly  be  confined  in  it,  then  closed  it  by  a 
stop-cock,  so  that  no  air  could  possibly  return. 


*  American  Artisan  ;    Locomotive,  1880. 


ENERGY  STORED  IN  SUPERHEATED   WATER.     85 

(6.)  I  boiled  water  in  an  open  boiler  for  several 
hours,  and  filled  a  bottle  half  full,  closed  and  sealed  it 
up,  so  that  when  it  became  cool  it  would  in  effect  be  un- 
der a  vacuum,  agitating  it  as  often  as  seemed  necessary. 

(7.)  Another  bottle  was  filled  with  the  same,  and 
sealed. 

(8.)  I  next  took  some  clean,  solid  ice,  dissolved  it 
under  oil,  and  brought  it  to  a  boil,  which  was  continued 
for  an  hour  or  more,  after  which  it  was  tightly  corked. 

(9.)  I  procured  a  bottle  of  carefully  distilled  water, 
after  long  boiling  and  having  been  perfectly  excluded 
from  air  during  the  distillation. 

(10.)  I  obtained  a  large  number  of  small  fish,  placed 
them  in  pure,  clean  water  in  an  open-headed  cask  on  a 
moderately  cold  night,  so  that  very  soon  it  became 
frozen  over,  consequently  excluding  the  air,  the  fish 
breathing  up  the  air  in  the  water,  so  that  (if  I  am  cor- 
rect in  this  theory)  a  water  freed  from  air  would  be  the 
result ;  but  in  some  of  these  different  processes,  if  not 
in  all,  I  was  likely  to  free  the  water  from  air,  if  it  could 
ever  possibly  occur  in  the  ordinary  course  of  operating 
a  steam  boiler. 

Having  procured  a  good  supply  of  glass  boilers 
adapted  to  my  purpose,  and  so  made  that  the  slightest 
changes  could  be  noted,  and  using  as  delicate  thermome- 
ters as  I  could  obtain,  I  took  these  samples  one  after 
another,  and  brought  them  to  the  boiling  point;  and 
every  one,  with  no  variation  whatever,  boiled  effectually 
and  positively  at  212°  Fahrenheit  or  under ;  nor  was 


86  STEAM  BOILER  EXPLOSIONS. 

there  the  slightest  appearance  of  explosion  to  be  ob- 
served." 

This  evidence  is,  of  course,  purely  negative. 

The  superheating  of  water,  on  even  the  small  scale  of 
the  laboratory  experiments  of  Donny,  Dufour  and  others, 
has  never  been  successfully  performed  except  with  the 
most  elaborate  precautions.  The  vessel  containing  the 
liquid  must  be  absolutely  clean ;  the  washing  of  all  sur- 
faces with  an  alkaline  solution  seems  to  be  one  of  the 
customary  preliminary  operations.  The  vessel  must 
usually  be  heated  in  a  bath  of  absolutely  uniform  tem- 
perature in  order  that  currents  may  not  be  set  up  within 
the  body  of  the  liquid  to  be  heated ;  no  solid  can  be 
permitted  to  enter  or  come  in  contact  with  it;  no  shock 
can  be  allowed  to  affect  it ;  even  contact  with  a  bubble 
of  gas  may  stop  the  process  of  superheating.  All  these 
conditions  are  as  far  removed  as  possible  from  those 
existing  in  steam-boilers. 

20.  The  Spheroidal  State,  or  Leidenfrost's  phe- 
nomenon, as  it  is  often  called,  is  a  condition  of  the 
water,  as  to  temperature,  precisely  the  opposite  of  that 
last  described,  its  temperature  being  less,  rather  than 
greater,  than  that  due  the  pressure  ;  while  the  adjacent 
metal  is  always  greatly  overheated,  and  thus  becomes  a 
reservoir  of  surplus  heat-energy  which  can  be  trans- 
ferred, at  any  instant,  to  the  water.  This  peculiar  phe- 
nomenon was  first  noted  by  M.  Leidenfrost  about  1 746. 


THE  SPHEROIDAL  STATE.  87 

It  was  studied  by  Klaproth,  Rumford,  and  Baudrimont,* 
and  more  thoroughly  by  Boutigny. 

When  a  small  mass  of  liquid  rests  upon  a  surface  of 
metal  kept  at  a  temperature  greatly  exceeding  the  boil- 
ing point  of  the  liquid  under  the  existing  pressure,  the 
fluid  takes  the  form  of  a  globule  if  a  very  small  mass, 
or  of  a  flattened  spheroid  or  round-edged  disk  if  of 
considerable  volume,  and  floats  around  above  the  metal, 
quite  out  of  contact  with  the  latter,  and  gradually,  very 
slowly,  evaporates.  The  higher  the  temperature  of  the 
plate,  the  more  perfect  this  repulsion  of  the  liquid. 
Should  the  temperature  of  the  metal  fall,  on  the  other 
hand,  the  globule  gradually  sinks  into  contact  with  it, 
and,  at  a  temperature  which  is  definite  for  every  liquid, 
and  is  the  lower  as  it  is  the  more  volatile,  finally  sud- 
denly absorbs  heat  with  great  rapidity  and  evaporates 
often  almost  explosively.  If  contact  is  forcibly  produced 
at  the  higher  temperature  of  the  supporting  plate  of 
metal,  as  under  a  blacksmith's  hammer,  a  real  explosion 
takes  place,  throwing  drops  of  the  liquid  in  every  direc- 
tion. 

M.  Boutigny  found  the  temperature  of  contact  to  be, 
for  water,  alcohol,  and  ether,  respectively,  142°  C,  134° 
and  61°  (287°  F.,  273,  and  142°).  In  all  cases,  the 
temperature  of  the  liquid  was  independent  of  that  of 
the  metal  and  somewhat  below  the  boiling  point.  It  is 
found,  also,  that  a  real  and  powerful  repulsion  is  pro- 
duced between  metal  and  liquid ;  this  is  supposed  to  be 

*  Ann.  de  Chemie  et  de  Physique,  2d  Series,  t.  Ixi. 


88  STEAM  BOILER   EXPLOSIONS. 

due,  in  part  at  least,  to  the  cushion  of  vapor  there 
interposing  itself.  Contact  is  accelerated  by  the  intro- 
duction of  soluble  salts  into  the  liquid. 

It  is  supposed  by  many  writers  that  this  phenomenon 
may  play  its  part  in  the  production  of  explosions  of 
steam-boilers,  and  especially  in  cases  in  which  there 
seems  some  evidence  that,  immediately  before  the  explo- 
sion, there  was  no  apparent  overheating  of  the  parts 
exposed  to  the  action  of  the  fire,  and  in  those  still  more 
remarkable  instances  in  which  the  shattered  parts  had 
been,  to  all  appearance,  much  stronger  than  other  por- 
tions which  had  not  been  ruptured,  no  evidence  existing 
of  low-water  or  overheating  at  the  furnace,  and  the 
pressure  being,  the  instant  before  the  accident,  at  or 
below  its  usual  working-figure.  Bourne  *  has  no  doubt 
that  this  does  sometimes  take  place.  Colburn  gives  a 
number  of  instances  of  explosions  taking  place  under, 
apparently,  precisely  similar  conditions,  and  Robinson  t 
also  cites  several,  in  some  of  which  the  plates  of  the  shell 
were  badly  shattered,  as  by  a  concussive  force.  In  some 
such  instances,  evidence  of  overheating,  but  only  far 
below  the  water-level  known  to  have  existed  immedi- 
ately before  the  explosion,  have  been  observed,  indicat- 
ing repulsion  to  have  there  occurred.  This  latter  is 
simply  still  another  instance  of  bringing  about  the  same 
results  as  when  pumping  water  into  an  overheated 
boiler  in  which  the  water  is  low. 

*  Treatise  on  the  Steam  Engine,  1868. 
f  Steam  Boiler  Explosions,  p.  33. 


THE  SPHEROIDAL  STATE.  89 

Mr.  Robinson  *  tells  of  a  case  in  which  a  nearly  new 
locomotive,  standing  in  the  house,  with  a  pressure,  as 
shown  but  a  moment  before  by  the  steam-guage,  of  but 
40  pounds — one-third  its  presumed  safe  working-press- 
ure— the  fire  low  and  everything  perfectly  quiet — 
exploded  witn  terrible  violence,  shattering  the  top  of 
the  boiler,  directly  over  the  fire-box,  into  many  parts. 
That  such  explosions  might  occur,  were  the  metal  actu- 
ally overheated  under  water,  is  shown  by  experiences 
not  at  all  uncommon. 

In  the  work  of  determining  the  temperatures  of  cast- 
ing alloys  tested  by  the  Author  t  for  the  U.  S.  Board 
appointed  in  1875  to  test  iron,  steel,  and  other  metals, 
at  the  first  casting,  composed  of  94.10  copper,  5.43  tin, 
while  pouring  of  the  metal  into  the  water  for  the  test, 
an  explosion  took  place  which  broke  the  wooden  vessel 
\vhich  held  the  water,  and  threw  water  and  metal 
about  with  great  violence.  It  appears  probable  that 
the  metal  was  heated  to  an  unusually  high  temperature, 
as  in  pouring  other  metals  when  at  a  dazzling  white 
heat  explosions  sometimes  took  place,  but  they  were 
usually  not  violent  enough  to  do  more  than  make  a 
slight  report  as  the  hot  metal  touched  the  water. 
Another  bar  was  cast  at  an  extremely  high  temperature, 
being  at  a  dazzling  white  heat.  On  pouring  a  small 
portion  in  water  in  attempting  to  obtain  the  tempera- 
ture, a  severe  explosion  took  place,  and  this  was  repeated 

*  Steam  Boiler  Explosions,  p.  62. 

f  Report  on  Copper-Tin  Alloys,  Washington,  1879. 


9o  STEAM  BOILER  EXPLOSIONS. 

every  time  that  even  a  small  drop  of  the  molten  metal 
touched  the  water.  The  cold  ingot  mould  was  then 
filled  with  this  very  hot  metal.  After  the  metal  remain- 
ing in  the  crucible  had  stood  for  several  minutes  and 
had  cooled  considerably,  it  could  be  poured  into  water 
without  causing  the  slightest  explosion.  Thus  it  would 
seem  that  the  temperature  at  which  contact  with  the 
water  is  produced  may  have  an  important  effect  upon 
the  violence  with  which  the  steam  is  generated,  and  also 
that  of  the  explosion  so  produced.  The  explosions  some- 
times taking  place  with  fatal  effect  in  foundries  when 
molten  metal  is  poured  into  damp  or  wet  moulds  are 
produced  in  the  manner  above  illustrated.  They  are 
usually  apparently  of  the  "fulminating  class."  Another 
instance  occurred  within  the  cognizance  of  the  Author, 
even  more  striking  than  either  of  the  above.  * 

Feb.  2,  1 88 1,  two  workmen  in  a  gold  and  silver 
refinery  were  engaged  in  "  graining  "  metal,  which  pro- 
cess consists  in  pouring  a  small  stream  of  melted  metal 
into  a  barrel  of  water,  while  a  stream  of  water  is  also 
run  into  the  barrel  to  agitate  the  water  already  there. 
Suddenly  an  explosion  occurred  which  literally  shivered 
the  barrel  and  threw  the  workmen  across  the  room. 
Every  hoop  of  the  barrel,  stout  hickory  hoops,  was 
broken.  The  staves,  seven-eighths  of  an  inch  thick, 
and  of  oak,  were  not  only  splintered  but  broken  across, 
and  the  bottom,  which  was  resting  on  a  flat  surface,  and 
which  was  of  solid  oak,  an  inch  in  thickness,  was  split 

*  Reported  in  the  Providence  (R.  I.)  Journal,  Feb.  2,  1881. 


THE  SPHERO/DAL  STATE.  91 

and  broken  across  the  grain.  A  box,  on  which  stood 
the  man  who  was  pouring  the  metal,  was  converted  into 
kindling-wood.  The  metal,  though  scattered  some- 
what, for  the  most  part  remained  in  place,  but  the  water 
was  thrown  in  all  directions. 

This  explosion  of  an  open  barrel,  like  the  preceding 
cases,  was  evidently  due  to  the  deferred  thermal  reaction 
of  the  water  with  a  mass  of  very  highly  heated  metal, 
with  which  it  was  finally  permitted  to  come  in  contact 
at  a  temperature  which  allowed  an  explosive  formation 
of  steam.  This  class  of  explosions,  by  which  open 
vessels  are  shattered  and  the  water  contained  in  them 
"atomized"  are  by  many  engineers  believed  to  exem- 
plify the  terrific  "  explosions  fulminantes  "  of  French 
writers  on  this  subject.  The  temperature  of  maximum 
vaporization,  with  iron  plates,  was  reported  by  the 
committee  of  the  French  Institute  to  be  346^°  F. 
(175°  C),  and  that  of  repulsion  385°  F.  (196°  C),  and 
to  be  the  same  under  all  pressures.  Any  cause  which 
may  retard  the  passage  of  heat  from  the  iron  to  the 
water,  though  but  the  thinnest  film  of  sediment,  grease, 
or  scale,  may  permit  such  increase  of  temperature  as 
may  lead  to  repulsion  of  the  water,  the  overheating  of 
the  metal,  the  production  of  the  spheroidal  condition, 
and  the  accidents  due  to  that  phenomenon,  provided 
that  the  fire  be  so  driven  as  to  supply  more  heat  than 
can  be  disposed  of  in  ordinary  working  by  the  circula- 
tion and  vaporization  then  going  on.  Robinson's 
experiments  with  safety-plugs  indicate  that  a  good  irra- 
diation is  usually  a  sufficient  insurance  against  this 


92  STEAM  BOILER  EXPLOSIONS. 

action  ;  and  experience  with  the  boilers  of  locomotives 
and  of  torpedo-boats,  in  which  from  50  to  100  pounds 
of  coal  per  squa-re  foot  (244  to  488  kilogs.  on  the  square 
metre)  of  grate  are  burned  every  hour,  shows  that  the 
risk,  with  clean  boilers  of  good  design,  is  not  great. 
With  impure  water  and  defective  circulation,  Robinson 
observed  many  instances  of  singular  and  dangerous 
phases  of  this  action.  *  It  is  suggested  that  many 
explosions  of  locomotives  on  the  road,  or  at  stations, 
may  be  due  to  the  impact,  on  the  shells  of  their  boilers, 
of  water  thus  projected  from  overheated  iron  below  the 
water-line.  In  many  such  cases,  the  engines  have  not 
left  the  rails,  the  break  taking  place  just  back  of  the 
smoke-box,  or  near  the  fire-box,  and  from  the  impact 
of  water  thus  thrown  from  the  tube-sheets. 

M.  Melsen  t  experimentally  proved  it  possible  to  pre- 
vent the  occurrence  of  the  spheroidal  condition  by  the 
distribution  of  spurs,  or  points  of  iron  over  the  endan- 
gered sheets. 

The  conductivity  of  the  metal  has  been  an  important 
influence  on  the  effect  of  contact,  suddenly  produced, 
between  the  red-hot  solid  and  the  liquid.  Professor 
Walter  R.  Johnson  observed,  in  his  elaborate  experi- 
ments, f  that  brass  produced  much  greater  agitation 
of  the  water  when  submerged  at  the  red-heat  than  did 
iron.  He  also  noted  the  singular  fact  that  water  at  the 

*  See  his  Steam  Boiler  Explosions,  pp.  40-46. 

t  Bull,  de  1' Academic  Royale  de  Belgique,  April,  1871. 

\  Reports  on  Steam  Boilers,  H.  R.,  1832,  p.  HI. 


THE   SPHEROIDAL    STATE.  93 

boiling  point,  thrown  upon  red-hot  iron,  requires  more 
time  for  evaporation  than  cold  water,  probably  in  con- 
sequence of  the  greater  efficacy  of  the  latter  in  bringing 
down  the  temperature  of  the  metal  to  that  of  maximum 
rapidity  of  action.  The  contact  with  the  iron  of 
incrustation,  oxide,  or  other  foreign  matter,  accelerated 
this  process,  also.  Johnson  found  that,  beyond  the 
temperature  of  maximum  repulsion,  vaporization  was 
accelerated  by  further  elevation  of  temperature. 

At  the  meeting  of  the  British  Association  in  1872, 
Mr.  Barrett  read  a  paper  upon  the  conditions  affecting 
the  spheroidal  state  of  liquids  and  their  possible  rela- 
tionship to  steam-boiler  explosions.  The  presence  of 
alkalies  or  soaps  in  water  perceptibly  aids  in  the  production 
of  the  spheroidal  state.  A  copper  ball  immersed  in 
pure  water  produced  a  loud  hissing  sound  and  gave  off 
a  copious  discharge  of  steam.  On  adding  a  little  soap 
to  the  water,  the  ball  entered  the  liquid  quietly.  Albu- 
men, glycerine,  and  organic  substances  generally  pro- 
duced the  same  result.  The  best  method  is  to  use  a 
soap  solution,  and  to  plunge  into  this  a  white-hot  cop- 
per ball  of  about  two  pounds  of  weight  The  ball 
enters  the  liquid  quietly,  and  glow  white  hot  at  a  depth 
of  a  foot  or  more  beneath  the  surface.  Even  against 
such  pressure,  the  ball  will  be  surrounded  with  a  shell 
of  vapor  an  inch  in  thickness.  The  reflection  of  the 
light  from  the  bounding  surfaces  of  the  vapor  bubble 
surrounding  the  glowing  ball,  gives  to  the  envelope  the 
appearance  of  burnished  silver.  As  the  ball  gradually 
cools,  the  bounding  envelope  become  thinner,  and  finally 


94 


STEAM  BOILER  EXPLOSIONS. 


collapses  with  a  loud  report  and  the  evolution  of  large 
volumes  of  steam.  Mr.  Barrett  makes  the  suggestion 
that  the  traces  of  oil,  or  other  organic  matters  which 
find  their  way  into  a  steam-boiler,  may  similarly  pro- 
duce a  sudden  generation  of  steam  sufficient  to  account 
for  certain  problematical  explosions,  and  thus  lends  some 
strong  confirmatory  evidence  to  the  idea  often  promul- 
gated by  others  within  and  without  the  engineering 
profession. 

21.  Steady  Rise  in  Pressure  has  been  shown  by 
the  experiments  of  the  committee  of  the  Franklin  Insti- 
tute and  by  numerous  cases  of  explosion,  both  before 
and  since  their  time,  to  be  capable  of  producing  very 
violent  explosions.  In  such  cases,  the  steam  being 
formed  more  rapidly  than  it  is  given  exit,  the  pressure 
steadily  increases  until  a  limit  is  found  in  the  final  rup- 
ture of  the  weakest  part  of  the  boiler.  Should  this 
break  occur  below  the  water-line  and  be  the  result  of 
local  decay  or  injury,  no  explosion  may  ensue;  but 
should  the  rupture  be  extensive,  or  should  it  occur 
above  or  near  the  surface  of  the  water,  the  succession  of 
phenomena  described  by  Clark  and  Colburn  may  follow, 
and  an  explosion  of  greater  or  less  violence  may  take 
place.  The  intensity  of  the  effect  will  depend  largely 
upon  the  quantity  of  stored  energy  liberated,  and  partly 
upon  the  suddenness  with  which  it  is  set  free.  A  slowly 
ripping  seam,  or  gradually  extending  crack,  would  per- 
mit a  far  less  serious  effect  than  the  general  shattering 
of  the  shell,  or  an  instantaneously  produced  and  exten- 
sive rent. 


STEADY  KISE  Itf  PRESSURE.  95 

The  time  required  to  produce  a  dangerous  pressure  is 
easily  calculated  when  the  weight  of  water  present,  Wy 
the  range  of  temperature  above  the  working  pressure 
and  temperature,  t\  —  /2>  and  the  quantity  of  heat,  Q, 
supplied  from  the  furnace  are  known,  and  is 


- 
Q 

Professor  Trowbridge  gives  the  following  as  fair  illus- 
rations  of  such  cases  :  * 

(i  .)     A  marine  tubular  boiler  of  largest  size,  such  that 

w=79,ooo  Ifes.  of  water. 

Suppose  the  working  pressure  to  be  2^,  and  the 
dangerous  pressure  4  atmospheres. 

The  boiler  contains  6,000  square  feet  of  heating  sur- 
face; and  supposing  the  evaporation  to  be  3  ibs.  of 
water  per  hour  for  each  square  foot,  we  shall  have,  tak- 
ing 1,000  units  of  heat  as  the  thermal  equivalent  of  the 
evaporation  of  I  fib.  of  water, 

/i-/=29°  F. 
„    5000x3X1000 
3*        ~6b~ 


60 


g6  STEAM  BOILER  EXPLOSIONS. 

(2.)  A  locomotive  boner,  containing  5,000  Bbs.  of 
water,  having  1  1  square  feet  of  grate-surface,  and  burn- 
ing 60  fbs.  of  coal  per  hour  on  each  square  foot  of  grate, 
each  pound  of  coal  evaporates  about  7  fbs.  of  water 
per  hour,  making  77  ibs.  of  water  evaporated  per 
minute. 

Suppose  the  working  pressure  to  be  90  ifts.  and  the 
dangerous  pressure  to  be  175  ; 

/i-/=50°  F. 

5000x50 
77x1000 

(3.)  The  Steam  Fire-  Engine.  —  The  boiler  contains 
338  fbs.  of  water  and  157  square  feet  of  heating-sur- 
face. Supposing  each  square  foot  of  heating-  surface  to 
generate  i  ife.  of  steam  in  one  hour,  the  pressure  will 
rise  from  100  to  200  Ifcs.  in 

T=J  minutes. 

(4.)  To  find,  in  the  same  boiler,  how  long  a  time 
will  be  required  to  get  up  steam  ;  that  is,  to  carry  the 
pressure  to  100  Ifos.  If  we  suppose  but  \y2  cubic  feet 
of  water  in  the  boiler,  we  shall  have 


minutes< 


157X1000 

~6o~ 
Thus,  if  W  is  diminished,  the  time  /  is  diminished  in  the 


STEADY  RISE  IN  PRESSURE.  97 

same  proportion.  The  lowering  of  the  water-level  from 
failure  of  the  feed-apparatus  increases  the  danger,  not 
only  by  exposing  plates  to  overheating,  but  by  causing 
a  more  rapid  rise  of  pressure  for  a  given  rate  of  com- 
bustion. Gradual  increase  of  pressure  can  never  take 
place  if  the  safety-valve  is  in  good  order,  and  if  it  have 
sufficient  area. 

The  sticking  of  the  safety-valve,  either  of  its  stem 
or  to  its  seat,  the  bending  of  the  stem,  or  the  jamming  of 
the  valve  by  a  superincumbent  object  or  lateral  strain, 
and  similar  accidents,  have  produced,  where  boilers  were 
strong  and  otherwise  in  good  order,  some  of  the  most 
terrific  explosions  of  which  we  have  records.  The  parts 
of  the  boiler  have  been  thrown  enormous  distances,  and 
surrounding  buildings  and  other  objects  levelled  to  the 
ground;  while  the  report  has  been  heard  miles  away 
from  the  scene  of  the  disaster. 

The  records  of  the  Hartford  company,  up  to  1887, 
include  accounts  of  26  explosions  of  vessels  detached 
from  the  generating  boiler,  used  at  moderate  pressures, 
for  various  purposes  in  the  arts,  and  there  have  been 
many  others  of  less  importance  that  were  not  consid- 
ered worthy  of  public  mention.  It  is  concluded  that 
the  percentage  of  explosions  among  bleaching,  digest- 
ing, rendering,  and  other  similar  apparatus  is  ten  times 
greater  than  among  steam-boilers  at  like  average  press- 
ures, and  the  destructive  work  done  is  quite  as  astonish- 
ing as  that  by  the  explosion  of  ordinary  steam  genera- 
tors. * 

1  he  Locomotive,  i88> 


98  STEAM  BOILER  EXPLOSIONS. 

This  is  sufficiently  decisive  of  the  question  whether  it 
is  possible  to  produce  destructive  explosions  simply  by 
excess  of  pressure  above  that  which  the  vessel  is  strong 
enough  to  withstand.  In  these  cases,  low- water,  and 
all  the  other  special  causes  operating  where  fire  and  high 
temperature  exist,  and  such  absurd  theories  as  the  gen- 
eration of  gas,  or  the  action  of  electricity,  are  elimi- 
nated, and  it  is  seen  that  mere  deterioration  and  loss  of 
strength,  or  a  rise  of  steam-pressure,  even  where  there 
is  an  ample  supply  of  water,  may  produce  explosions  of 
the  utmost  violence. 

22.  The  Relative  Safety  of  Boilers  of  the  various 
types,  is  determined,  mainly,  by  their  general  design 
and  their  greater  or  less  liability  to  serious  and  exten- 
sive injury  by  the  various  accidents  and  methods  of  de- 
terioration to  which  all  are  to  a  greater  or  less  extent 
liable.  The  two  essential  principles  by  which  to  com- 
pare and  to  judge  the  safety  of  boilers,  are  : 

(i).  Steam-boilers  should  be  so  designed,  con- 
structed, operated,  inspected  and  preserved,  as  not  to  be 
liable  to  explosion. 

(2).  Boilers  should  be  so  designed  and  constructed 
that,  if  explosive  rupture  occurs  at  all,  it  shall  be  with 
a  minimum  of  danger  to  attendants  and  surround- 
ing objects. 

The  prevention  of  liability  to  explosion  and  the  pro- 
vision against  danger  should  explosion  actually  take 
place,  are  the  two  directions  in  which  to  look  for 
safety. 

As  Fairbairn  has  remarked,  the  danger  does  not  con- 


THE  RELATIVE  SAFETY  OF  BOILERS. 


99 


sist  in  the  intensity  of  the  pressure,  but  in  the  character 
and  construction  of  the  boiler.*  Other  things  being 
equal,  that  boiler,  or  that  form  of  boiler,  in  which  the 
original  surplus  strength  of  form  and  detail  is  greatest, 
and  which  is  at  the  same  time  best  preserved,  is  the 
safest.  That  class  in  which  original  strength  is  most 
certainly  and  easily  preserved,  has  an  important  advan- 
tage ;  those  boilers  in  which  facilities  for  constant  over- 
sight, inspection  and  repairs  are  best  given,  are  superior 
in  a  very  important  respect  to  others  deficient  in  those 
points.  For  example,  the  cylindrical  tubular  boiler,  if 
properly  set,  is  very  accessible  in  all  parts,  and  may  be 
at  all  times  examined  ;  it  offers  peculiar  facilities  for  in- 
spection and  the  hammer-test,  and  can  be  readily  kept 
in  repair ;  but  it  is  liable,  in  case  of  its  becoming  weak- 
ened by  corrosion  over  any  considerable  area,  or  along 
any  extended  line  of  lap,  to  complete  disruptive  explo- 
sion. 

On  the  other  hand,  the  various  "  sectional,"  or  so- 
called  "safety"  boilers,  are  rarely  as  convenient  of  ac- 
cess or  of  inspection,  and  cannot  usually  be  as  readily 
and  completely  cleaned ;  but  they  are  so  designed  and 
constructed  as  to  be  little,  if  at  all,  liable  to  dangerous 
explosive  rupture,  and  if  a  tube  or  other  part  bursts,  it 
is  not  likely  to  endanger  life  or  property.  That  boiler 
is,  therefore,  on  the  whole,  best  which  is  least  liable  to 
those  kinds  of  injury  which  lead  to  explosion,  and  which 
is  least  likely  to  do  serious  harm  should  explosion  actu- 

*Engineering  Facts  and  Figures,  1865. 


ioo  STEAM  BOILElt  EXPLOSIONS, 

ally  take  place.*  Those  who  select  the  tubular  boiler 
are  commonly  influenced  mainly  by  considerations  of 
cost,  and  the  first  of  the  above  considerations ;  while 
the  users  of  the  water-tube  sectional  boilers  are  con- 
trolled by  the  second,  so  far  as  either  considers  this 
form  of  risk  at  all. 

During  the  experiments  of  Jacob  Perkins,  about  1825 
and  later,  the  value  of  the  "  sectional  "  boilers,  where 
high  pressures  are  adopted,  was  well  shown.  He  fre- 
quently raised  his  steam-pressure  to  one  hundred  atmos- 
pheres^ and  in  his  earlier  work  rupture  often  took  place, 
but  no  ill  effects  followed.  The  division  of  the  boiler 
into  numerous  compartments  saved  the  attendants  from 
injury.  In  a  letter  to  Dr.  T.  P.  Jones,  dated  March  8, 
1827,1  Mr.  Perkins  states  that  he  had  worked  at  the 
above-mentioned  pressure,  with  a  ratio  of  expansion  of 
12;  his  usual  pressure  was  about  two-thirds  that 
amount,  and  the  ratio  of  expansion  8.  Mr.  Perkins 
was  then  building  an  engine  to  safely  carry  a  pressure 
of  2,000  pounds  per  square  inch.^ 

23.  Defective  Designs,  causing  explosion,  are  not 
as  common  as  many  other  causes.  They  exist,  how- 
ever, more  frequently  than  is  probably  usually  supposed. 
The  delects  are  generally  to  be  observed  in  the  staying 

*Dr.  E.  Alban,  following  John  Stevens,  was  probably  the  first  to  en- 
nunciate  the  principle  :  "  So  construct  the  boiler  that  its  explosion  may 
not  be  dangerous."  The  High-Pressure  Steam-Engine,  1847,  p.  70. 

f  Jour.  Franklin  Institute,  V^l.  3;  p.  415. 

\  Ibid,  p.  412. 

§  Reports  on  Steam  Boiler?,  H.  R.,  1832,  p.  188. 


DEFECTIVE  DESIGNS.  ioi 

of  such  boilers  as  require  bracing;  in  the  insertion  of 
the  heads  of  plain  cylindrical  boilers ;  in  the  attachment 
of  drums  and  the  arrangement  of  man-holes  and  hand- 
holes,  and,  less  frequently,  in  the  selection  of  the  proper 
thickness  and  quality  of  iron  for  the  shells  and  flues. 
Such  defects  as  these  are  the  most  serious  possible ; 
they  are  not  only  serious  in  themselves,  and  at  the  start, 
but  are  of  a  kind  which  is  commonly  very  certain  to  be 
exaggerated  and  rendered  continually  more  dangerous 
with  age.  A  thin  shell  grows  constantly  thinner,  a 
weak  stay  or  brace  weaker,  and  an  unstayed  head  more 
likely  to  yield  every  day ;  while  a  flue  originally 
too  thin  is  all  the  time  overstrained,  not  simply  by  the 
steam-pressure,  but  also  by  the  action  of  the  relatively 
stronger  parts  around  it.  The  most  minute  study  of 
every  detail,  and  the  most  careful  calculation  of  the 
strength  of  every  part,  with  an  allowance  of  an  ample 
factor  of  safety,  are  the  essentials  to  safety  in  design. 

Faulty  design  in  bracing  is  illustrated  by  an  explo- 
sion which  took  place  in  New  York  City,  January  1 5th, 
1 88 1,  by  which,  fortunately,  however,  no  loss  of  life  was 
caused.  A  dome-head,  proportioned  and  braced  as 
shown  in  the  next  figure,  was  blown  out,  and  tore  up  a 
side-walk  under  which  the  boiler  was  set,  doing  no 
other  damage.  The  case  was  reported  on  by  Mr.  Rose, 
substantially  as  follows : 

"  The  dome-crown,  tearing  around  the  edge,  at  A,  also 
tore  across  at  B,  being  thus  completely  severed.  The 
iron  at  the  fractures  was  of  excellent  quality.  The  plate 


102 


STEAM  BOILER  EXPLOSIONS. 


showed  lamination  in  places,  and  the  crack  around  A 
was  rusty  and  evidently  not  of  recent  formation. 

The  six  stays,  three  of  which  are  shown  in  place  at  C, 
Fig-  *3»  were  aU  in  position  in  the  dome,  and  their  sur- 


FIG.  13. — DOME  AND  HEAD. 

faces  of  contact  with  the  dome  were  covered  by  a  black 
polish  indicating  movement  and  abrasion. 


FIG.  14. — EXPLOSION  OF  DOME. 

Apparently,  as  the  pressure  and  temperature  increased 
and  decreased  the  dome-head  might  lift  and  fall,  bend- 


DEFECTIVE  DESIGNS. 


103 


ing  on  A  as  a  center.  Thus  taking  I  as  a  center,  the 
movement  of  C  would  be  in  the  direction  of  F,  while  at 
D  the  direction  would  be  toward  J,  and  the  direction  of 
motion  of  the  two  would  nearly  coincide. 

The  exploded  dome  shows  an  indentation  at  I,  due  to 
the  motion  of  the  foot  of  the  stay. 

Another  error  in  the  design  of  this  boiler  is  that  the 
diameter  of  the  dome  shell  is  34  inches,  and  a  circle  of 
iron  about  1 8  inches  in  diameter  is  punched  out  of  the 


FIG.  15. — DEFECTIVE  FORM. 

shell  at  D.  This  opening  is  required  only  to  admit  an 
inspector  or  workman  to  the  interior  of  the  boiler,  hence 
it  is  several  inches  wider  than  it  should  be. 

Defective  design  is  illustrated  in  the  case  of  the  boiler, 


104 


STEAM  BOILER  EXPLOSIONS. 


the  explosion  of  which  left  it  in  the  form  shown   in  the 


engraving.* 


This  boiler  consisted  of  two  incompletely  cylindrical 
shells,   united  as  in   the  next  figure,   and    ineffectivel)' 


\ 


FIG.  16. — JUNCTION  OF  SHELLS. 

stayed  at  the  lines  of  contact.  This  is  a  form  which, 
insufficiently  braced,  becomes  peculiarly  dangerous. 
In  the  case  illustrated,  the  braces  yielded,  after  having 
been  weakened  by  continual  alteration  of  form,  and 
split  the  two  shells  apart  as  seen.  It  is  probably  possible 
to  brace  boilers  of  this  type  safely,  but  it  is  safer  to 
avoid  their  use.  They  have  sometimes  been  used  for 
marine  purposes,  where  lack  of  space  compelled  special 
expedients,  the  bracing  consisting  of  strong  bolts  with 
nuts  and  washers  on  the  outside  of  the  shell;  a  compar- 
atively strong  and  safe  construction. 

Steam-domes  are  a  source  of  some  danger  and  of  ad- 
ditional expense,  however  well  designed  and  attached, 
and  it  is  probably  good  economy,  all  things  considered, 
to  dispense  with  them  altogether,  using  a  dry- pipe,  in- 
stead, and  expending  the  amount  of  their  entire  cost  on 
an  increase  in  size  of  boiler  over  that  which  would  have 
otherwise  been  selected.  The  large  boiler  will  steam 
easier  and  more  regularly,  will  give  dryer  steam,  and 
will  be  less  liable  to  dangers  of  deterioration  or  of  ex- 

*  Locomotive  Feb.,  1880. 


DEFECTIVE  DESIGNS.  105 

plosion.  A  steam-drum  above  the  boiler  and  connect- 
ed by  two  separate  nozzles,  or  a  drum  connecting  the 
several  boilers  of  a  battery  is  not  subject  to  the  objec- 
tions which  apply  to  the  attached  dome. 

24.  Defective  Construction,  material  and  work- 
manship are  responsible  for  many  explosions  of  steam- 
boilers. 

Thin,  laminated,  or  blistered  sheets,  imperfect  welds 
in  bracing,  the  strains  produced  by  the  drift-pin,  care- 
lessness in  the  attachment  of  nozzles  and  drums,  and  in 
neglect  of  the  precaution  of  straightening  man-holes 
and  hand-holes,  and  bad  riveting,  are  all  common 
causes  of  weakness  and  accidents.  Only  the  most 
careful  and  skillful,  as  well  as  conscientious  builders, 
can  be  relied  upon  to  avoid  all  such  faults,  and  to  turn 
out  boilers  as  strong  and  safe  as  the  designs  may  per- 
mit. In  all  cases,  careful  and  unintermitted  inspection 
by  an  experienced,  competent  and  trustworthy  inspec- 
tor, should  be  provided  for  by  the  proposing  purchaser 
and  user  of  the  boiler.  In  the  case  of  some  of  the  more 
modern  forms  of  boiler,  constructed  under  a  system  of 
manufacture  which  includes  some  machine  fitting  and 
working  to  gauge  of  interchangeable  parts,  with  regular 
inspection  before  assemblage,  this  supervision  becomes 
less  essential,  and  a  careful  test  and  trial  previous  to  ac- 
ceptance, may  be  all  that  is  necessary  to  insure  a  satisfac- 
tory and  safe  construction.  Whenever  defective  material 
or  bad  workmanship  is  detected,  the  fault  should  always 
be  corrected  before  the  boiler  is  accepted,  and  previous  to 
any  trial  or  use  under  steam.  Careless  riveting  and  the 


io6  STEAM  BOILER  EXPLOSIONS. 

use  of  the  drift-pin  are  defects  which  cannot  often  be 
readily  detected  afterward,  and  they  are  such  common 
causes  of  explosion  that  too  much  care  cannot  be  taken 
to  avoid  any  establishment  of  which  the  reputation,  in 
this  regard,  is  not  the  best. 

Defective  welds,  the  cause  of  many  unfortunate  acci- 
dents following  the  yielding  stays  or  braces,  are  among 
the  most  common  and  least  easily  detected  of  all  faults. 
They  are  due  to  the  difficulty  of  producing  metallic  con- 


FIG.  17. — DEFECTIVE  WELDING. 

tact  in  abutting  surfaces  between  which  particles  of 
scale  and  superficial  oxidation  may  interpose.  The 
grain  of  the  iron,  as  illustrated  in  the  accompanying 
engraving,  is  broken  at  such  junctions,  and  it  is  difficult  to 
secure  a  good  weld,  and  next  to  impossible  to  determine 
until  it  actually  breaks,  whether  it  is  seriously  unsound. 
Defective  workmanship  is  often  exhibited  most  strik- 
ingly by  the  distorted  forms  of  rivets,  revealed  after  ex- 
plosion has  caused  a  fracture  along  the  seams,  or  when 
the  yielding  of  the  weakened  seam  has  resulted  in  an 
explosion.  The  following  illustrations  of  a  variety  of 


DEFECTIVE   CONS TR  UCTION. 


107 


cases  of  such  distortion,  all  taken  from  a  single  boiler,* 
show  how  very  serious  this  kind  of  defect  may  be.  It 
is  not  to  be  presumed  that  such  carelessness,  or  worse, 
as  is  here  exemplified,  is  to  be  attributed  to  the  builder 
himself,  but  rather  to  the  fault  of  the  workmen  care- 
fully concealing  their  action  from  the  eye  of  the  foreman 
or  inspector.  No  law  or  rule  can  protect  the  purchaser 
from  this  kind  of  fault;  his  only  reliance  must  be  upon 
the  reputation  of  the  maker  and  his  workmen,  and  the 
vigilance  and  skill  of  his  inspector. 

FIG.  1 8. — Rivet  "driven"  in  over-set 
holes,  the  conical  point  broken  off  by  the 
tearing  apart  of  the  plates,  the  head  nearly 
severed  from  the  body,  and  probably 
weakened  in  driving. 

FlG.  19.— Rivet  "driven" 
in  over-set  roles,  heads  bro- 
ken off  by  the  tearing  apart  of  the  plates, 
conical  point  also  nearly  broken  off,  bad 
sample  of  "  driving,"  cone  too  flat  to  pro- 
perly hold  down  the  plate.  FlG-  J9- 

The  next  figure  illustrates  a  group  of  similar  distorted 
rivets  which  played  their  part  in  the  production  of  an 
explosion. 

In  these  instances  it  is  seen  that  the  defective  rivet 
is  usually  evidence  of  either  exceedingly  bad  workman- 
ship in  spacing  and  in  assembling  the  sheets,  the  use 
of  the  drift-pin  being  shown,  or  of  equally  bad  work  in 
riveting  up.  Modern  machine-work  is  seldom  produc- 
tive of  such  defects. 


FIG.  18. 


*  Locomotive,  Feb.  1880. 


STEAM  BOILER  EXPLOSIONS. 


FIG.  20. — DEFECTIVE  RIVETS. 
F!G.   21. — Rivet   "driven"    in    slightly 
over-set   holes,    point   eccentric    and    not 
symmetrical,    too    flat    to   properly  secure 
the  edge  of  the  plate. 

FlG.  22: — Rivet  "  driven  "  in 
badly     over-set     holes,     very 
FIG.  21.       weak.      See   Figs.    23,  24  and 
25,  which  were  "  sheared"  at  the  time  of  the 
explosion.      The   dark    shading   on    lower 
end  Fig.  22  indicates  an  old  crack. 

FiGS.  23,  24,  25. — Samples  selected  from  a  number 
taken  from  a  "sheared"  seam,  which  was  believed  to  be 


FIG.  22. 


FIG.  23.  FIG.  24.  FIG.  25. 

the  initial  break  from  which  the  explosion  arose.     They 
were  no  doubt  similar  to  Fig.  22  before  they  gave  way. 


DEFECTIVE  CONSTRUCTION. 


109 


The  Author,  on  one  occasion,  picked  out  with  his 
fingers  twelve  consecutive  rivets,  deformed  like  those 
here  illustrated,  from  a  torn  seam  in  an  exploded  boiler. 
FlG.  26. — Rivet  "  driven  "  in  over-set 
holes;  it  was  probably  fractured  under 
the  head  in  driving.  Taken  from  a  seam 
that  was  broken  through  the  rivet  holes. 

FlGS.  27  and  28. — Long  rivets   taken 
from  a  broken  casting  which  they  were  in- 
tended to  secure  to  the  wrought-iron  head 
of  the   boiler.     The  holes  in   the  wrought-iron  plate 
were  "  drifted  "  and  chipped  to  allow  the  rivets  to  en- 
ter,  as  shown  by  the  enlarged  portion   of  the   body- 


FIG.  26. 


FIG.  27. 


FIG.  28. 


This  irregular  upsetting  and  the  sharp  little  wave  or  iron 
on  the  body  of  Fig.  27  indicate  the  thickness  of  die 
wrought-iron  plate. 


HO  STEAM  BOILER  EXPLOSIONS, 

25.  Developed  Weakness,  usually  a  consequence 
of  progressing  decay  by  corrosion,  is  the  most  common 
of  all  causes  of  the  explosion  of  steam-boilers.  A 
boiler,  designed  and  constructed  of  the  best  possible  pro- 
portions and  of  the  best  of  materials,  having  at  the 
start  a  real  factor  of  safety  of  six,  may  be  assumed  to 
be  as  safe  against  this  kind  of  accident  as  possible  ;"but, 
with  the  beginning  of  its  life,  decay  also  begins,  and  the 
original  margin  of  safety  is  continually  lessened  by  a 
never  ceasing  decay.  The  result  is  an  early  reduction 
of  this  margin  to  that  represented  by  the  difference 
between  the  working-pressure  and  that  fixed  as  a  max- 
imum by  the  inspector's  tests.  Should  this  difference 
be  sufficient  to  insure  against  accident,  resulting  from 
further  depreciation,  in  the  interval  between  inspector's 
or  other  tests,  explosion  will  not  occur;  should  this 
margin  not  be  sufficient,  danger  is  always  to  be  appre- 
hended, and,  almost  a  certainty  that  rupture,  and  possibly 
explosive  rupture,  will  at  some  time  occwr.  The  mar- 
gin is  legally,  usually  fifty  per  cent.;  it  is  too  small  to 
permit  the  proprietor  to  feel  a  real  security.  It  is 
usually  thought  that  the  tests  should  show  soundness 
under  pressure,  at  least  at  double  the  regular  working- 
pressure  at  which  the  safety-valve  is  set*  Many  cases 
have  been  known  in  which  the  boiler  has  yielded  at  the 

^Experiments  made  by  the  Author,  and  later,  by  other  investigators, 
have  indicated  the  possibility  that  an  apparent  factor  of  safety  of  two,  un- 
der load  momentarily  sustained,  may  not  actually  mean  a  factor  exceeding 
one  for  permanent  loading.  Materials  of  Engineering,  Vol.  I.,  §133' 
Vol.  II..  §295- 


DEVELOPED    WEAKNESS.  m 

working-pressure  not  very  long  after  the  regular  official 
inspection  had  taken  place. 

Such  an  example  was  that  of  the  explosion  of  the 
boiler  of  the  "  Westfield,"  in  New  York  harbor,  in  Ju-ne, 
1 876.  The  steam  ferry-boat  "  Westfield,'1  is  one  of  three 
boats  which  have  formed  one  of  the  regular  lines  between 
New  York  and  Staten  Island.  The  "  Westfield  "  made 
her  noon  trip  up  from  the  Island  to  the  city,  on  Sunday, 
July  3Oth,  and  while  lying  in  the  New  York  slip,  her 
boiler  exploded,  causing  the  death  of  about  one  hun- 
dred persons  and  the  wounding  of  as  many  more. 

The  boiler  is  of  a  very  usual  form,  as  represented  in 
Fig.  29,  and  is  known  as  a  "  Marine  return-flue  boiler." 
The  diameter  of  its  shell — the  cylindrical  part  was  rup- 
tured— is  ten  feet :  its  thickness,  No.  2  iron,  twenty- 
eight  hundredths  of  an  inch. 


FIG.  29. — BOILER  OF  THE  WESTFIELD. 

The  evidence  indicated  that  the  explosion  occurred 
in  consequence  of  the  existing  of  lines  of  channeling  and 
long  existing  cracks,  by  which  the  boiler  was  gradually 


1 1 2  STEAM  BOILF  ?  EXPLOSIONS. 

so  weakened,  that,  six  weeks  after  its  inspection  and 
test,  the  pressure  of  steam  being  allowed  by  the  engineer 
to  rise  slightly  above  the  pressure  allowed,  the  boiler 
was  ruptured,  giving  way  along  a  horizontal  seam 
and  tearing  a  course  out  of  the  boiler. 

The  common  lap-joint,  customarily  adopted  in  trve 
construction  of  boilers,  is  liable  to  such  serious  distortion 
under  very  heavy  pressure,  as  to  produce  leakage  be- 
fore actually  yielding,  and  this  leakage  is  sometimes  so 
great  as  to  act  as  a  safety-valve.  Thus,  suppose  a 
straight  strip  of  plate  riveted  up  in  parts  as  in  Fig.  30.* 
A  heavy  pull  will  cause  distortion  as  shown,  in  all  cases 
except  where  a  butt-joint  is  made  with  a  covering  string 
on  each  side.  If  the  metal  is  brittle,  and  the  rivet-heads 
strong,  preventing  the  bending  of  the  plate  on  the  line 
of  rivet-holes,  the  plate  will  probably  break  adjacent  to 
G  or  F,  Fig.  30;  or  in  the  middle,  I  and  H.  But  should 
the  plates  be  ductile  or  the  rivet-heads  weak,  the  break 
would  occur  at  the  line  through  the  holes. 


FIG.  30. — YIELDING  JOINTS. 

If  the  plates,  Fig.  30,  A,  etc.,  were  straight  at  the 
joint,  the  extreme  end,  L,  must  contract  and  the  outer 
one  expand  at  M,  involving  in  the  one  a  compression  or 
upsetting,  and  in  the  other  drawing  the  metal.  If  the 

*  See  Locomotive,  Oct.,  1880. 


DEVELOPED    WEAKNESS. 


joint  be  a  butt,  with  a  single  outer  cover,  C,  a  similar 
contraction  must  take  place  at  both  ends  and  a  con- 
traction of  the  middle  of  the  covering  strip,  while  the 
opposite  would  take  place  in  the  case  of  the  joint  with 
the  inner  cover,  B  ;  these  distortions  are  not  likely  to 
take  place  in  a  transverse  seam  of  a  cylindrical  boiler 
shell  from  internal  pressure.  The  butt-joint,  with  two 
covering-plates,  E,  would  retain  its  shape. 

The  next  Figures,  31,  33,  show  the  effect  of  strain  on 
rivet-holes,  and  on  holes  filled  by  the  rivet.     Lapped 


FIG.  31.  Belore  Stretching,   FIG.  32.  After  StretcMng. 

longitudinal  joints  are  shown  at  A',  Fig.  30.  Single- 
riveted  and  single-covered  butts  at  B'  and  C'.  D'  shows 
a  double-riveted  single-covered  butt. 

Multiple  Explosions  are  not  infrequent.  They 
usually  occur  in  consequence  of  the  explosion  of  one  of 
a  battery,  with  the  result  of  injuring  adjacent  boilers  in 
such  a  manner  that  they  explode,  the  phenomena  fol- 
lowing each  other  so  quickly,  as  to  produce  the  appear- 
ance of  simultaneous  explosion.  It  is  possible,  also, 
that,  in  some  cases,  an  accession  of  pressure  in  a 
set  of  boilers,  may  take  place  with  such  suddenness  as 
to  explode  several,  notwithstanding  there  may  exist  a 
difference  in  their  resisting  power ;  the  weakest  not  be- 


1 14  STEAM  BOILEP  EXPLOSIONS. 

ing  given  time  to  act  as  a  safety  valve  to  the  rest.  It  is 
doubtful,  however,  whether  such  cases  can  often,  if  ever, 
arise. 

26.  General  and  Local  Decay  introduces  vastly 
different  degrees  and  elements  of  danger.  As  has  been 
elsewhere  stated,  in  effect,  an  explosion  comes  of  extend- 
ed rupture;  while  local  injuries  or  breaks,  if  they  do  not 
lead  to  wider  injury,  cannot  cause  widespread  disaster. 
Hence,  general  corrosion,  extending  over  considerable 
areas  of  plate,  or  along  lines  of  considerable  length,  is  a 
cause  of  danger  of  complete  disruption  and  explosion. 
A  corroded  spot  in  a  fire-box,  a  loosened  rivet,  or  even 
a  broken  stay,  if  the  boiler  be  otherwise  well-propor- 
tioned, well-built,  and  in  good  order,  may  not  be  a 
serious  matter,  but  a  thinned  sheet  in  the  shell,  a  long 
groove  tinder  a  lap,  a  line  of  loose  rivets,  or  a  cluster  of 
weakened  stays  or  braces,  will  certainly  be  most  dan- 
gerous. General  or  widespread  corrosion  is  very 
liable  to  lead  to  explosion;  local  and  well-guarded  cor- 
rosion may  cut  quite  through  the  metal  and  simply 
cause  a  leak  or  an  unimportant  "  burst."  Old  fire- 
boxes are  often  seen  covered  with  "  patches  "  in  places, 
and  yet  they  very  rarely  explode.  Such  a  state  of  af- 
fairs may,  nevertheless,  by  finally  producing  large  areas 
of  patched  and  fairly  uniformly  weak  portions  of  the 
boiler,  lead  to  precisely  the  conditions  most  favorable 
to  explosion.  A  steam-boiler  experimentally  exploded 
at  Sandy  Hook,  N.  J.,  Sept.,  1871,*  had  previously,  by 

~-5  journal  Franklin  Institute,  Jan.,  1872. 


GENERAL  AND  LOCAL  DECAY.  ti$ 

repeated  rupture,  by  hydraulic  pressure  and  patching, 
been  gradually  brought  into  precisely  this  state,  and  ex- 
ploded under  steam  at  53^  pounds,  about  four  atmos- 
pheres pressure,  a  slightly  lower  pressure  than  it  had 
sustained  (5  9  pounds)  at  its  last  test.  On  this  occasion, 
when  a  pressure  was  reached  of  50  pounds  per  square 
inch,  a  report  was  heard  which  was  probably  caused  by 
the  breaking  of  one  or  more  braces,  and  at  53^  pounds, 
the  boiler  was  seen  to  explode  with  terrible  force.  The 
whole  of  the  enclosure  was  obscured  by  the  vast  masses 
of  steam  liberated;  the  air  was  dotted  with  the  flying 
fragments,  the  largest  of  which — the  steam  drum — -rising 
first  to  a  height  variously  estimated  at  from  200  to  400 
feet,  fell  at  a  distance  of  about  450  feet  from  its  original 
position.  The  sound  of  the  explosion  resembled  the  re- 
port of  a  heavy  cannon.  The  boiler  was  torn  into  many 
pieces,  and  comparatively  few  fell  back  upon  their  origi- 
nal position. 


FIG.  33. — CORROSION. 

Thus  corrosion  may  affect  a  single  spot  in  a  boiler,  in 
hich  case  a  "  patch,"  if  properly  applied,  Should  make 


Il6  STEAM  BOILER  EXPLOSIONS. 

the  boiler  nearly  as  strong  as  when  whole.  A  series  of 
weak  spots  near  each  other  may  so  weaken  a  boiler  as 
to  produce  explosion,  as  may  any  considerable  area  of 
thin  plate,  although,  when  occuring  in  the  stayed  sur- 
faces of  a  fire-box,  the  metal  may  become  astonishingly 
thin.  A  sketch  of  spots  of  corrosion  is  shown  in  Fig. 
33,  which  represents  the  cause  of  an  actual  explosion. 
This  cause  of  explosion  may  be  either  internal  or  exter< 
nal,  and  is  produced  internally  by  bad  feed-water,  and 
externally  by  dampness  or  by  water  leaking  from  the 
boiler,  either  unseen  or  neglected.  It  is  always  dan- 
gerous to  have  any  portion  of  a  boiler  concealed  from 
observation. 

The  effect  of  covering  a  part  of  a  sheet  subject  to  cor- 
rosion by  solid  iron,  as  by  the  lap  of  a  seam,  is  shown  in 
the  next  figure,  which  also  exhibits  a  common  method 


FIG.  34. — CORROSION  AT  A  SEAM. 

of  corrosion  along  a  seam.  The  same  effect  is  seen  still 
more  plainly  in  the  succeeding  figure,  in  which  the  pit- 
ting which  so  often  attends  the  use  of  the  surface  con- 
denser is  also  well  shown. 


THE  METHODS  OF  DECAY. 


117 


FIG.  35. — PITTING. 

27.  The  Methods  of  Decay  are  as  various  as  the 
forms  and  locations  of  the  parts  subject  to  corrosion. 
As  Colburn*  has  said  "  As  a  malady,  corrosion  corres- 
ponds in  its  comparative  frequency  and  fatality,  to  that 
great  destroyer  of  human  life,  consumption,"  and  it  has 
as  innumerable  phases  and  periods  of  action.  The  two 
most  common  methods  of  decay  are  the  general,  and 
here  and  there  localized,  corrosion,  that  goes  on  in  all 
boilers,  and,  in  fact,  on  all  iron  exposed  to  air  and  car- 
bonic acid  presence  of  moisture ;  and  the  concentrated 
and  localized  oxidation  that  is  often  seen  along  the  line 
of  a  seam,  at  the  edge  of  the  lap,  where  the  continual 
changing  of  form  of  the  boiler  is  as  constantly  producing 
an  alternate  flexing  and  reflex  motion  of  the  sheet  which 
throws  off  the  oxide  as  fast  as  formed  along  that  line, 
and  exposes  fresh,  clean  metal  to  the  corroding  influence. 


*  Trans.  Brit.  Assoc.,  1884. 


Il8  STEAM  BOILER  EXPLOSIONS. 

A  groove  or  furrow  is  thus,  in  time,  produced,  which 
may,  as  occurred  in  the  cas^  of  the  "  Westfield,"  Fig. 
36,  actually  cut  through  the  sheet  before  explosion 
takes  place. 

The  phenomenon  known  as  "  grooving  "  or  "  furrow- 
ing" is  well  illustrated  by  the  case  just  mentioned,  in 
which  this  action  was  originally  started,  probably  by 
the  carelessness  of  the  workman,  who,  either  in  chipping 
the  edge  of  the  lap  along  a  girth  seam,  or  in  caulking 
the  seam,  scored  the  under  sheet  along  the  edge  of  the 
lap  with  the  corner  of  his  chisel,  or  with  the  caulking- 
tool.  This  is  a  very  common  cause  of  such  a  defect. 

The  boiler  was  broken  into  three  parts.  The  first,  and 
by  far  the  largest  part,  consisted  of  the  furnaces,  steam- 
chimney  and  flues,  with  a  single  course  of  the  shell ;  the 
second  consisted  of  two  courses  of  the  outside  shell  next 
the  back  head,  together  with  that  head,  to  which  they 
remained  attached ;  the  third  piece  consisted  of  a  single 
complete  course  from  the  middle  of  the  cylindrical  shell, 
which  was  separated  at  one  of  its  longitudinal  seams, 
partially  straightened  out  and  flung  against  the  bottom 
and  side  of  the  boat.  The  last  piece  remained  opposite 
its  original  position  in  the  boiler,  before  the  explosion, 
while  the  first  and  second  pieces  went  in  opposite  direc- 
tions, the  former  finally  lying  several  feet  nearer  the  en- 
gine than  when  in  situ,  and  against  the  timbers  of  the 
"  gallows-frame,"  while  the  latter  piece  was  thrown  fifty 
feet  forward  into  the  bow  of  the  boat,  where  it  fell,  torn 
and  distorted.  The  longitudinal  seam,  along  which 
piece  number  three  separated,  and  the  deep  score  or 


THE  METHODS  OF  DECAY. 


119 


"  channel  "  cutting  nearly  through  in  many  places,  and 
presenting  every  evidence  of  being  an  old  flaw,  were 
plainly  seen.  The  mark  made  by  a  chisel  in  chipping, 
and  that  of  the  caulking-tool,  were  seen,  and  indicated 
the  probable  initiative  cause  of  the  flaw. 

The  Author  examined  this  piece  and  found  an  old 
crack  or  "  channel "  cut,  along  the  edge  of  Jie  horizon- 
tal lap  referred  to  as  being  at  the  ends  of  the  sheet,  and 
in  some  places  so  nearly  through  that  it  was  difficult  to 
detect  the  mere,  scale  of  good  iron  left,  while  in  other 
places  there  remained  a  sixteenth  of  an  inch  of  sound 
metal.  Fig.  36  exhibits  a  section  of  the 
crack. 

Were  this  the  weakest  part  in  the 
boiler,  and  the  least  thickness  here  one- 
sixteenth  of  an  inch,  the  tensile  strength 
being  equal  to  the  average  determined 
by  the  tests  to  be  described,  the  pressure 
required  to  rupture  such  a  boiler,  ten 
feet  in  diameter,  would  be  44079X1-16 
X  2  4- 1 20=47  Iks.  per  square  inch,  near- 
ly. A  pressure  of  twenty-seven  pounds 
would  burst  it  open  where  the  least  thick- 
ness was  slightly  more  than  one-thirty-second  of  an  inch. 
One  portion  may  be  supported,  to  some  extent,  by  a 
neighboring  stronger  part.  Along  this  longitudinal 
seam  the  limit  of  strength  would  seem  to  have  been 
about  thirty  pounds  per  square  inch,  which  is  about  the 
pressure  at  which  the  boiler  exploded,  this  seam  ripping 
for  a  distance  of  several  feet. 


FIG.  36. 
GROOVING. 


\To  face  page  121.] 


THE  METHODS   OF  DECAY.  121 

Sometimes  this  action  produces  a  narrow  crack,  and 
at  other  times,  as  above  stated,  as  the  rust  formed  is 
thrown  or  scoured  off  the  iron  at  the  bend,  leaving  a 
comparatively  clean  surface,  oxidation  is  probably  accel- 
erated, and  the  fault  takes  the  form  of  a  groove  or  fur- 
row. If  unperceived,  this  goes  on  until  a  rupture  or  an 
explosion  occurs. 

Of  forty  explosions  of  locomotive  boilers  noted  in 
British  Board  of  Trade  reports,*  eighteen  gave  way  at 
the  fire-box  and  twenty  at  the  barrel.  Of  these  twenty, 
every  one  was  the  result  of  "  grooving"  or  cracks  along 
the  lap  of  seams,  all  of  which  were  lap-joints.  The 
grooves  were  most  common ;  they  always  occurred 
along  the  edge  of  the  inside  over- lap,  just  where  the 
changes  of  form  with  varying  pressure  would  concen- 
trate their  effects.  Such  results  are  sometimes  also 
seen  at  butt-joints,  especially  where  a  strip  has  been 
used  inside.  The  racking  action  of  the  engines  may 
produce  precisely  the  same  effect.  Wherever  change 
of  form  is  felt,  grooving  or  furrowing,  and  cracking,  may 
be  expected  to  be  found  in  time.  Where  the  boiler  is 
already  heavily  strained  along  one  of  these  lines  of  re- 
duced thickness,  any  slight  added  stiess,  as  ajar,  or  the 
action  of  a  caulking-tool,  as  where  leaks  in  boilers  under 
pressure  are  being  caulked,  may  precipitate  an  explo- 
sion, the  break  following  the  groove  or  crack  just  as  a 
stretched  drum-head  may  yield  to  the  scratch  of  a 
knife. 

*  Wear  and  Tear  of  Steam  Boilers  ;  F.  A.  Paget,  Trans.  Soc.  of  Arts, 
j86p.  London,  1865,  p.  8,  .. 


122  STEAM  BOILER  EXPLOSIONS. 

28.  Differences  in  Temperature  between  parts  of 
a  boiler  more  or  less  closely  connected  in  the  structure 
may  produce  serious  strains,  and  some  instances  of  explo- 
sion have  been  attributed  to  this  cause. 

Changes  of  temperature  ^ccur  as  steam  is  raised  or 
blown  off  from  a  boiler,  and  its  temperature  at  one  time 
becomes  that  due  the  steam-pressure,  and  then  it  falls 
to  that  of  the  atmosphere  each  time  that  steam  is  blown 
off.  It  will  change  its  form  more  or  less,  and  will  usually 
be  subjected  to  some  strain  by  this  process.  Again, 
while  actually  at  work,  the  steam-space  and  upper  por- 
tion of  the  water-space  are  at  the  temperature  of  steam 
at  the  working-pressure,  while  the  lower  part  is  contin- 
ually varying  in  temperature  from  that  of  the  feed- 
water  to  the  maximum  which  it  attains  after  entrance. 
This  difference  of  temperature  between  the  upper  and 
lower  parts  of  the  boiler,  as  well  as  between  other  por- 
tions, causes  a  continual  tendency  to  distortion,  and,  if 
this  distortion  be  resisted,  a  stress  is  thrown  upon  the 
parts  equal  to  that  which  would  be  required,  acting 
externally,  to  remove  the  distortion,  if  produced.  The 
stress  is  also  equal  to  the  mechanical  force  that  would  be 
necessary  to  produce  similar  distortion. 

Thus,  had  the  temperature  of  the  main  and  upper 
part  of  the  "  Westfield's  "  boiler  been,  after  the  entrance 
of  the  feed-water,  273°,  or  that  due  to  about  twenty- 
seven  or  twenty-eight  pounds  steam,  while  the  feed- 
water  having  a  temperature  of  73°,  the  bottom  of  the 
boiler  having  a  temperature,  in  consequence,  200°  below 
that  of  the  top,  the  difference  in  length  would  b^  about 


DIFFERENCES  IN    TEMPERATURE.  123 

one-eight-hundredth,  and,  if  confined  by  rigid  abut- 
ments, iron  so  situated  would  be  subject  to  a  stress  of 
twelve  and  a  half  tons  per  square  inch.  But,  in  this 
case,  one  part  would  yield  by  compression  and  the  other 
by  extension,  and  if  they  were  to  yield  equally  it  would 
reduce  the  stress  to  six  and  a  quarter  tons.  Actually, 
in  this  case,  the  lower  fourth  and  upper  three-fourths 
would  be  likely  to  act  against  ^ach  other,  and  the  stress, 
if  the  boiler  had  no  elasticity  of  form,  would  be  about 
nine  tons.  Any  elasticity  of  form — and  boilers  gener- 
ally possess  considerable — would  still  further  reduce  the 
strain,  and  it  very  frequently  makes  it  insignificant. 

It  is  thought,  by  more  experienced  engineers  and 
other  authorities,  that  many  of  the  explosions  known  to 
have  taken  place,  after  inspection  and  test,  at  pressures 
lower  than  those  of  the  test,  are  caused  by  the  weaken- 
ening  action  of  unequal  expansion,  the  stresses  and 
strains  produced  in  this  manner  being  superadded  to 
those  due  to  simple  pressure,  against  which  latter  the 
boiler  might  otherwise  have  been  safe.  Such  defects 
may  also  be  the  final  provocation  to  explosion  when 
cold  feed-water  is  pumped  into  a  boiler,  on  getting  up 
steam,  or  possibly,  sometimes,  when  cooling  off.  It  has 
even  been  asserted  that  an  empty  boiler  has  been  rup- 
tured by  such  changes  of  form  consequent  on  building 
a  light  fire  of  shavings  in  a  flue  to  start  the  scale.  The 
Author  has  known  of  instances  in  which  the  girth-seams 
of  large  new  marine  flue-boilers  were  ruptured  along  the 
line  of  rivet-holes  a  distance  of  several  feet  by  the  intro- 


124  STEAM  BOILER  EXPLOSIONS. 

duction  of  a  large  volume  of  cold  feed-water,  when 
steam  was  up,  but  the  engine  at  rest. 

The  differences  of  temperature  on  the  two  sides  of  the 
sheet  may  be  important.  While  it  is  true  that  the  heat 
supplied  by  the  furnace-gases  is  absorbed  by  the  boiler 
to  the  same  extent,  practically,  without  much  regard  to 
the  thickness  of  the  plates  of  the  boiler,  it  is  a  well- 
known  fact  that  the  resistance  of  iron  to  the  flow  of  heat 
is  so  great  that  the  effect  of  heat  on  the  metal  itself  is 
seriously  modified  by  the  thickness  of  the  sheet.  Heavy 
plates  "  burn "  away,  projecting  rivet-heads  are  de- 
stroyed and  the  laps  of  heavy  plates  are  especially  liable 
to  be  thinned  seriously  where  they  are  employed. 

A  variation  of  temperature  of  considerable  range,  and 
often  recurring,  frequently  causes  injury  by  hardening 
the  metal  of  the  boiler,  making  it  brittle  and  liable  to 
crack  with  change  of  form,  and  also  produces  the  very 
change  of  form  causing  this  cracking.  The  experiments 
of  Lt-Col.  Clark,  R.  A.,*  show  that  great  distortion 
may  be  thus  produced.  It  is  probably  thus  that  iron, 
and  especially  steel,  fire-boxes  so  often  crack,  in  conse- 
quence of  a  continual  swelling  of  the  metal  under  vary- 
ing temperatures  and  the  stresses  so  caused.  This 
action,  combined  with  oxidation,  external  and  internal, 
sometimes  makes  the  plates,  and  often  the  stays,  of  the 
boiler  remarkably  weak  and  brittle ;  they  sometimes 
become  more  like  cast  than  wrought-iron.  The  thicker 
the  sheet,  the  more  readily  is  it  overheated  and  over- 
strained. 

*  Proc.  Royal  Society,  1863  ;  Jour.  Franklin  Inst.,  1863. 


THE  MANAGEMENT  OF   THE   STEAM-BOILER.    125 

The  extent  to  which  alteration  of  form  under  pressure 
may  go,  with  good  material  before  actual  rupture,  is 
illustrated  by  the  following  :* 

During  the  summer  of  1868  a  cylindrical  boiler,  made 
of  i^  inch  steel  plates,  built  at  the  Fort  Pitt  Iron  Works, 
Pittsburgh,  was  tested  under  authority  of  the  govern- 
ment, with  a  view  to  determining  the  relative  advantages 
of  steel  and  iron  as  a  material  for  navy  boilers.  When 
the  pressure  of  cold  water  had  reached  780  Ibs.,  the 
"  girt "  of  the  boiler  was  found  to  have  permanently 
increased  3^  inches,  and  at  820  Ibs.,  rupture  occurred. 

Cases  have  been  known  in  which  a  steel  crown-sheet 
has  become  overheated,  and  has  sagged  down  until,  the 
tube-sheet  going  with  it,  a  basin-shaped  form  has  been 
produced,  convex  toward  the  fire,  and  yet  no  fracture 
produced,  even  when  the  pump  was  put  on  and  the 
boiler  filled  up  again  under  pressure. 

29.  The  Management  of  the  Steam-Boiler,  or, 
more  correctly,  its  mismanagement,  while  in  operation, 
and  a  neglect  of  proper  supervision  and  inspection,  may 
be  considered,  on  the  whole,  the  usual  reason  of  explo- 
sion, as  the  deterioration  of  the  boiler  is  the  immediate 
cause,  and  this  deterioration  is  almost  invariably  so 
gradual  and  so  readily  detected  by  intelligent  and  pains- 
taking examinations  that  there  is  rarely  any  excuse  for 
its  resulting  disastrously.  A  well-made  boiler,  under 
good  management  and  proper  supervision,  may  be  con- 
sidered as  practically  free  from  danger. 

*  Iron  Age,  Sept.  26,  1872. 


,26  STEAM  BOILER   EXPLOSIONS. 

The  person  in  direct  charge  of  the  boiler  is  usually 
a  presumably  experienced  and  trustworthy  man.  He 
should  be  thoroughly  familiar  with  his  business,  gener 
ally  intelligent,  of  good  judgment,  ready  and  prompt  in 
emergencies,  and  absolutely  reliable  at  all  times.  His 
first  duty  is  to  see  that  the  boiler  is  full  to  the  water- 
line,  trusting  only  the  gauge-cocks ;  he  must  keep  con- 
stant watch  of  the  furnaces,  flues  and  other  surfaces  sub- 
ject to  the  action  of  the  fire,  and  thus  be  certain  that  no 
injury  is  being  done  by  overheating  or  sediment ;  he 
must  keep  the  feed-apparatus  in  perfect  working  order, 
keep  up  the  supply  of  water  continuously  and  regularly, 
and  see  that  the  safety-valve  is  in  good  order  at  all  times. 
Such  careful  management,  conscientious  inspection  and 
cleaning,  and  repairing  at  proper  intervals,  will  insure 
safety. 

To  keep  the  safety-valve  in  good  working  order  and 
to  make  certain  that  it  is  operative,  provision  should  be 
made  for  opening  it  by  hand,  and  it  should  be  daily 
raised,  before  getting  up  steam,  to  the  full  height  of  its 
maximum  lift. 

Explosions  of  gas  sometimes  precipitate  steam-boiler 
explosions.  Should  the  gases  leaving  the  fuel  and  the 
furnace  not  be  completely  burned,  but  become  so  min- 
gled in  the  flues  as  to  produce  an  explosive  mixture, 
combustion  finally  occurring,  the  shock  may  be  sufficient 
to  cause  rupture  of  the  boiler,  and,  as  has  actually  some- 
times happened,  its  explosion.  Sewer  gases  have  been 
known  to  find  their  way  into  an  empty  boiler  through 
an  open  blow-off"  pipe,  and  have  been  exploded  by  the 


THE  MANAGEMENT  OF  THE  STEAM  BOILER. 


127 


first  light  brought  to  the  manhole,  and  with  serious 
damage  to  adjacent  property.  Mineral  oils  used  to 
detach  scale  have  caused  similar  dangerous  and  some- 
times fatal  explosions  by  the  ignition  of  the  mixture  of 
their  vapors  and  the  air  within  the  boiler.  It  is  import- 
ant that  care  be  taken  in  using  lights  about  boilers  in 
such  cases  of  application  of  mineral  oils. 

Explosions  of  gas  within  a  boiler  at  work  cannot 
occur ;  but  the  suggestion  of  the  possibility  of  such  an 
occurrence  is  often  made.  No  decomposition  of  water 
can  take  place  except  a  portion  of  the  boiler  is  over- 
heated; this  happening,  all  the  oxygen  produced  is 
absorbed  by  the  iron,  and  no  recombination  can  occur 
later,  even  were  it  possible  for  ignition  to  take  place 
under  the  conditions  producing  decomposition. 

The  flooding  of  a  boiler  with  water  until  it  is  filled  to 
the  steam-pipe,  or  safety-valve,  may  cause  so  serious  a 
retardation  of  the  outflow  of  the  mingled  fluids  as  to 
result  in  overpressure  and  great  danger.  Mr.  W.  L. 
Gold  *  gives  the  following  instances,  and  the  experience 
of  the  Author  justifies  fully  his  statement.  The  steam- 
pipe  or  the  safety-valve  cannot  relieve  a  full  boiler  rap- 
idly and  safely. 

First,  a  boiler  38  inches  in  diameter,  two  flues,  shell 
j£  inch  Juniata  iron,  ruptured  in  the  sheet  a  crack  9 
inches  long,  steam  gauge  indicating  60  Ibs.,  safety-valve 
weighted  at  80  Ib.  pressure.  This  rupture  closed  in- 
stantly, and  if  he  had  not  seen  it  made,  he  might  possi- 

*Am.  Manufacturer,  Feb.,  iSSi. 


I28  STEAM  BOILER  EXPLOSIONS. 

bly  have  been  surprised  by  an  explosion,  with  water 
and  steam  in  their  normal  condition,  very  shortly  after. 
Second,  a  steam-drum  (spanning  a  battery  of  five  boilers) 
30  inches  in  diameter.  The  blank-head  forced  (bulged) 
out,  the  I  y2  inch  stay-rods  stretched,  and  the  corner  of  the 
head-flange  cracked  one- third  around.  Third,  a  verti- 
cal boiler,  built  especially  to  carry  high  pressure  (safe 
running  pressure  150  Ibs.),  the  hand-hole  and  man-hole 
joints  forced  out  past  the  flanges,  the  steam-pipe  joints 
and  union  forced  out,  the  packing  in  the  engine  piston 
destroyed,  and  the  engine  generally  racked,  so  as  to  be 
almost  useless.  Steam  pressure  by  gauge  from  40  to 
60  Ibs.;  safety-valve  weighted  at  90  Ibs. 

Mr.  Gold  suggests  that,  as  this  is  a  not  infrequent  oc- 
currence, many  explosions  may  be  simply  the  final  act  in 
the  drama  commenced  by  the  feed-pump. 

30.  Emergencies  must  be  met  with  a  clear  head 
and  ready  wit,  with  perfect  coolness,  and,  usually,  with 
both  promptness  and  quickness  of  action.  Every  man 
employed  about  steam-boilers,  as  well  as  every  engineer 
and  every  proprietor,  should  have  carefully  thought  out 
the  proper  course  to  take  in  any  and  every  emergency 
that  he  can  conceive  of  as  likely  or  possible  to  arise,  and 
should  have  constantly  in  mind  the  means  available  for 
meeting  it  successfully.  When  the  time  comes  to  act, 
it  is  not  always,  or  even  often,  possible  to  take  time  to 
study  out  the  best  thing  to  be  done;  action  must  be 
taken,  on  the  instant,  based  on  earlier  thought  or  on 
either  the  intuition  or  the  impulse  of  the  moment. 

"  Low-water"  presents,  perhaps,  the  most  common, 


EMERGENCIES.  1 29 

as  well  as  one  of  the  most  serious,  of  such  emergencies. 
The  instant  it  is  detected,  the  effort  must  be  made 
to  check  the  fall  to  a  lower  level ;  the  fire  must  be 
dampened,  preferably  by  throwing  on  wet  ashes,  and 
the  boiler  allowed  to  cool  down.  Care  should  be  taken 
that  the  safety-valve  is  not  raised  so  as  to  produce  a 
priming  that  might  throw  water  over  the  heated  metal, 
and  that  no  change  is  made  in  the  working  of  either  en- 
gine or  boiler  that  shall  produce  foaming  or  an  in- 
creased pressure.  If,  on  examination,  it  is  found  that 
the  water  has  not  fallen  below  the  level  of  either  the 
crown- sheet  or  any  other  extended  area  of  heating  sur- 
face, the  pump  may  be  put  on  with  perfect  safety ;  but 
if  this  certainty  cannot  be  assured,  the  boiler  should  be 
cooled  down  completely,  and  carefully  inspected  and 
tested,  and  thoroughly  repaired,  if  injured.  If  no  part 
of  the  exposed  metal  is  heated  to  the  red-heat  there  is 
no  danger,  except  from  a  rise  in  the  water-level  and 
flooding  the  hot  iron.  If  any  portion  should  be  red- 
hot,  an  additional  danger  is  due  to  the  steam-pressure, 
which  should  be  reduced  by  continuing  the  steady  work- 
ing of  the  engine  while  extinguishing  the  fire.  If  the 
safety-valve  be  touched  at  such  a  time,  it  should  be 
handled  very  cautiously,  allowing  the  steam  to  issue 
very  steadily  and  in  such  quantities  that  the  steam- 
gauge  hand  shows  no  fluctuation,  while  steadily  falling. 
The  damping  of  the  fire  with  wet  ashes  will  reduce  the 
temperature  and  pressure  very  promptly  and  safely. 
The  Author  has  experimentally  performed  this  opera- 
tion, standing  by  a  large  outside-fired  tubular  boiler  while 


I3o 


STEAM  BOILER  EXPLOSIONS. 


all  the  water  was  blown  out,  and  then  covering  the  fire. 
The  pyrometer  inserted  in  the  boiler  showed  no  eleva- 
tion of  temperature  until  all  the  water  was  gone,  and 
the  fire  was  then  so  promptly  covered  that  the  rise 
was  but  a  few  degrees  and  the  boiler  was  not  injured. 
As  it  proved,  there  was  not  the  slightest  danger  in  that 
case ;  but  with  less  promptness  of  action  some  danger 
might  have  arisen  of  injuring  the  boiler,  although  not  of 
explosion. 

Overheated  plates,  produced  by  sediment,  or  over- 
driving, resulting  in  the  producing  of  "  pockets  "  or  of 
cracks,  are,  virtually,  cases  of  low- water,  and  the  action 
taken  should  be  the  same.  The  boiler  being  safely 
cooled  down,  the  injured  plate  should  be  replaced  by  a 
sound  sheet,  all  sediment  or  scale  carefully  removed, 
and  a  recurrence  of  the  causes  of  the  accident  effectively 
provided  against. 

Cracks,  suddenly  appearing  in  sheets  exposed  to  the 
fire  or  elsewhere,  sometimes  introduce  a  serious  danger. 
The  steps  to  be  taken  in  such  a  case  are  the  immediate 
opening  of  the  safety-valve  and  reduction  of  steam- 
pressure  as  promptly  and  rapidly  as  possible,  meantime 
quenching  the  fire  and  then  cooling  ofif  the  boiler  and 
ascertaining  the  extent  of  the  injury  and  repairing  it. 
In  such  a  case,  unless  the  crack  is  near  the  safety-valve 
itself,  no  fear  need  be  entertained  of  too  rapid  discharge 
of  the  steam. 

Blistered  sheets  should  be  treated  precisely  as  in  the 
case  preceding.  It  is  not  always  possible  to  surmise  the 
extent  of  the  injury  or  the  damage  involved  until 


EMERGENCIES.  131 

steam  is  off  and  an  examination  can  be  made.  It  is  not, 
however,  absolutely  necessary  to  act  as  promptly  as  in 
the  preceding  cases ;  and,  when  the  blister  is  not  large 
and  is  not  extending,  it  is  sometimes  perfectly  allowable 
to  await  a  convenient  time  for  blowing  off  steam  and 
repairing  it. 

An  inoperative  safety-valve,  either  stuck  fast,  or  too 
small  to  discharge  all  the  steam  made,  or  to  keep  the 
pressure  down  to  a  safe  point,  produces  one  of  the  most 
trying  of  all  known  emergencies.  In  such  a  case,  steam 
should  be  worked  off  through  the  engine,  if  possible, 
and  discharged  through  any  valves  available,  through 
the  gauge-cocks,  or  even  through  a  few  scattered  rivet- 
holes,  out  of  which  the  rivets  may  be  knocked  on  the 
instant ;  the  fire  being  in  the  meantime  checked  by  the 
damper,  or  by  free  use  of  water.  The  throwing  of  water 
into  a  furnace  is  often  a  somewhat  hazardous  operation, 
however,  and,  if  necessary,  should  be  performed  with 
some  caution,  to  avoid  risk  of  injury  of  either  the  per- 
son attempting  it  or  of  the  boiler.  The  use  of  wet 
ashes  is  preferable.  In  all  cases  in  which  it  is  to  be 
attempted  to  reduce  the  rate  of  generation  of  heat, 
closing  the  ashpit- doors  as  well  as  opening  the  fire- 
doors  will  be  of  service  by  checking  the  passage  of  hot 
air  from  below  and  accelerating  the  influx  of  cold  air 
above  the  grate  ;  but  the  closing  of  the  ashpit  involves, 
with  a  hot  fire,  some  risk  of  melting  down  the  grates. 

31.  The  Results  of  Explosions  of  steam-boilers,  in 
spreading  destruction  and  death  in  all  directions,  are  so 
familiar  as  scarcely  to  require  illustration ;  but  a  few 


132  STEAM  BOILER  EXPLOSIONS. 

instances  may  be  described  as  examples  in  which  the 
stored  energy  of  various  types  of  boiler  has  been  set 
free  with  tremendous  and  impressive  effect. 

Referring  to  the  table  in  $  7,  and  to  case  No.  I  : 
The  explosion  of  a  boiler  of  this  form  and  of  the  pro- 
portions here  given,  in  the  year  1843,  in  the  establish- 
ment of  Messrs.  R.  L.  Thurston  &  Co.,  at  Providence, 
R.  L,  is  well  remembered  by  the  Author.  The  boiler-house 
was  entirely  destroyed,  the  main  building  seriously  dam- 
aged, and  a  large  expense  was  incurred  in  the  purchase 
of  new  tools  to  replace  those  destroyed.  No  lives  were 
lost,  as  the  explosion  fortunately  occurred  after  the 
workmen  had  left  the  building.  A  similar  explosion  of 
a  boiler  of  this  size  occurred  some  years  later,  within 
sight  of  the  Author,  which  drove  one  end  of  the 
exploding  boiler  through  a  1 6-inch  wall,  and  several 
hundred  feet  through  the  air,  cutting  off  an  elm  tree 
high  above  the  ground,  where  it  measured  9  inches  in 
diameter,  partly  destroying  a  house  in  its  further  flight, 
and  fell  in  the  street  beyond,  where  it  was  found  red  hot 
immediately  after  striking  the  earth.  Long  after  the 
Author  reached  the  spot,  although  a  heavy  rain  was  fall- 
ing, it  was  too  hot  to  be  touched,  and  was  finally,  nearly 
two  hours  later,  cooled  off  by  a  stream  of  water  from  a 
hose,  in  order  that  it  might  be  moved  and  inspected. 
It  had  been  overheated,  in  consequence  of  low-water, 
and  cold  feed-water  had  then  been  turned  into  it.  The 
boiler  was  in  good  order,  but  four  years  old,  and  was 
considered  safe  for  IIO  pounds.  The  attendant  was 
seriously  injured,  and  a  pedestrian  passing  at  the  instant 


THE  RESULTS   OF  EXPLOSIONS.  133 

of  the  explosion  was  buried  in  the  ruins  of  the  falling 
walls  and  killed.  The  energy  of  this  explosion  was 
very  much  less  than  that  stored  in  the  boiler  when  in 
regular  work. 

A  boiler  of  class  No.  3,  which  the  Author  was  called 
upon  to  inspect  after  explosion,  had  formed  one  of  a 
"battery"  often  or  twelve,  and  was  set  next  the  out- 
side boiler  of  the  lot.  Its  explosion  threw  the  latter 
entirely  out  of  the  boiler-house  into  an  adjoining  yard, 
displaced  the  boiler  on  the  opposite  side,  and  demolished 
the  boiler-house  completely.  The  exploding  boiler  was 
torn  into  many  pieces.  The  shell  was  torn  into  a  heli- 
cal ribbon,  which  was  unwound  from  end  to  end.  The 
furnace-end  of  the  boiler  flew  across  the  space  in  front 
of  its  house,  tore  down  the  side  of  a  "  kier-house,"  and 
demolished  the  kiers,  nearly  killing  the  kier-house  at- 
tendant, who  was  standing  between  two  kiers.  The 
opposite  end  of  the  boiler  was  thrown  through  the  airf 
describing  a  trajectory  having  an  altitude  of  fifty  feet, 
and  a  range  of  several  hundred,  doing  much  damage  to 
property  en  route,  finally  landing  in  a  neighboring  field- 
The  furnace-front  was  found  by  the  Author  on  the  top  of 
a  hill,  a  quarter  of  a  mile,  nearly,  from  the  boiler-house. 
The  attendant,  who  was  on  the  top  of  the  boiler  at  the 
instant  of  the  explosion,  opening  a  steam-connection  to 
relieve  the  boiler,  then  containing  an  excess  of  steam  and 
a  deficiency  of  water,  was  thrown  over  the  roof  of  the 
mill,  and  his  body  was  picked  up  in  the  field  on  the 
other  side,  and  carried  away  in  a  packing-box  measuring 
about  two  feet  on  each  side.  The  cause  was  low- water 


134 


STEAM  BOILER   EXPLOSIONS. 


and  consequent  overheating,  and  the  introduction  of 
water  without  first  hauling  the  fires  and  cooling  down. 
Both  this  boiler  and  the  plain  cylinder  are  thus  seen  to 
have  a  projectile  effect  only  to  be  compared  to  that  of 
ordnance. 

The  violence  of  the  explosion  of  the  locomotive 
boiler  is  naturally  most  terrible,  exceeding,  as  it  does, 
that  of  ordnance  fired  with  a  charge  of  150  pounds  of 
powder  of  best  quality,  or  perhaps  250  pounds  of  ordi- 
nary quality  fired  in  the  usual  way.*  On  the  occasion 
of  such  an  explosion  which  the  Author  was  called  upon 
to  investigate,  in  the  course  of  his  professional  practice, 
the  engine  was  hauling  a  train  of  coal  cars  weighing 
about  1000  tons.  The  steam  had  been  shut  off  from  the 
cylinders  a  few  minutes  before,  as  the  train  passed  over 
the  crest  of  an  incline  and  started  down  the  hill,  and  the 
throttle  again  opened  a  few  moments  before  the  explo- 
sion. The  explosion  killed  the  engineer,  the  fireman, 
and  a  brakeman,  tore  the  fire-box  to  pieces,  threw  the 
engine  from  the  track,  turning  it  completely  around, 
broke  up  the  running  parts  of  the  machinery,  and  made 
very  complete  destruction  of  the  whole  engine.  There 
was  no  indication,  that  the  Author  could  detect,  of  low- 
water  ;  and  he  attributed  the  accident  to  weakening  of 
the  fire-box  sheets  at  the  lower  parts  of  the  water-legs 
by  corrosion.  The  bodies  of  the  engineer  and  fireman 
were  found  several  hundred  feet  from  the  wreck,  the 

*  The  theoretical  effect  of  good  gunpowder  is  about  500  foot-tons  per 
pound  (340  toum-metres  per  kilogramme),  according  to  Noble  and  Able 


THE  RESULTS  OF    EXPLOSIONS. 


'35 


former  among  the  branches  of  a  tree  by  the  side  of  the 
track.  This  violence  of  projection  of  smaller  masses 
would  seem  to  indicate  the  concentration  of  the  energy 
of  the  heat  stored  in  the  boiler,  when  converted  into 
mechanical  energy,  upon  the  front  of  the  boiler,  and  its 
application  largely  to  the  impulsion  of  adjacent  bodies. 
The  range  of  projection  was,  in  one  case,  fully  equal  to 
the  calculated  range.  The  energy  expended  is  here 
nearly  the  full  amount  calculated. 


FIG.  37. — EXPLOSION  OF  BOILERS. 
BROOKLYN,  N.  Y. 

Figures  37,  38,  39,  40  illustrate  the  explosion  of  two 
large  boilers  which   produced  very  disastrous   effects,* 


*  Scientific  American,  May  20,  1882. 


136 


STEAM  BOILER  EXPLOSIONS. 


killing  the  attendant  and  destroying  the  boiler-house 
and  other  property. 

These  boilers  were  horizontal,  internally-fired,  drop- 
flue  boilers,  seven  feet  diameter  and  twenty-one  feet 
long,  the  shells,  single  riveted,  originally  five-sixteenths 
of  an  inch  thick. 

The  two  exploded  boilers  were  made  twenty-one 
years  before  the  explosion,  and  worked,  as  their  makers 
intended,  at  about  thirty  pounds  per  square  inch,  until 
about  twenty  months  before  the  explosion,  at  which 
time  additional  power  was  required,  and  the  pressure 
was  increased  to,  and  limited  at,  fifty  pounds. 


FIG.  38. — POSITION  OF  THE  THREE  BOILERS  AFTER  THE  EXPLOSION. 

A  third  boiler  did  not  explode,  but  was  thrown  about 
fifty  feet  out  of  its  bed. 

A  few  minutes  before  noon,  while  the  engine  was 
running  at  the  usual  speed,  the  steam-gauge  indicating 
forty-seven  pounds  pressure,  and  the  water-gauges  show- 
ing the  usual  amount  of  water,  the  middle  one  exploded; 


THE   RESULTS   OF  EXPLOSIONS. 


137 


the  shell  burst  open  and  was  nearly  all  stripped  off.     The 
remainder  of  the  boiler  was  thrown  high  in  the  air. 

While  this  boiler  was  in  the  air,  No.  I,  the  left-hand 
boiler,  having  been  forcibly  struck  by  parts  of  No.  2, 
also  gave  way,  so  that  its  main  portion  was  projected 
horizontally  to  the  front,  arriving  at  the  front  wall  of 
the  building  in  time  to  fall  under  No.  2,  as  shown  in 
Fig.  38.  The  most  probable  method  of  rupture  is  indu 
cated  in  Fig.  38,  as  the  line  A  B  separates  a  ring  of 
plates  which  was  found  folded  together  beneath  the  pile 
of  debris.  If  the  initial  break  had  been  at  some  point 
on  the  bottom,  this  belt  of  plates  would  have  been 
thrown  upward  and  flattened,  instead  of  downward, 
where  it  was  folded  by  the  flood  of  water  from  No.  I 
boiler. 


FIG.  39. — INITIAL  RUPTURE. 

The  third  boiler  was  raised  from  its  bed  by  the  issuing 
water,  and  thrown  about  fifty  feet  to  the  right  of  its 
original  position. 

These  two  boilers  contained  probably  more  than  four- 
teen tons  of  water,  which  had  a  temperature  due  to 
forty-seven  pounds  of  steam,  and  the  effect  of  its  sud- 


138 


STEAM  BOILER   EXPLOSIONS. 


den  liberation  equalled  that  of  several  hundred  pounds  of 
exploded  gunpowder. 


FIG.  40. — INTERIOR  OF  BOILER-HOUSE  PRIOR 
TO  EXPLOSI  )N. 

The  terrible  wreck  usually  consequent  upon  the  ex- 
plosion of  a  locomotive  boiler  is  well  illustrated  in  the 


FIG.  41. — EXPLODED  LOCOMOTIVE. 

accompanying  engraving,  which  represents  the  result  of 
such  an  explosion  on  the  Fitchburg  railway,  August  13. 


THE  RESULTS    OF  EXPLOSIONS.  139 

1877,  while  the  havoc  wrought  among  the  tubes  on  such 
an  occasion  is  as  strikingly  illustrated  in  the  next  figure. 
In  the  case  of  an  explosion  of  a  locomotive  investigated 
by  a  commission  of  which  the  Author  was  a  member, 
the  train  was  moving  slowly  when  the  boiler  exploded 
with  a  loud  report ;  the  locomotive  was  turned  compkfrly 


FIG.  42. — TUBES  OF  AN  EXPLODED  BOILER. 

over  backward,  carrying  with  it  the  fireman,  and  bury- 
ing him  beneath  the  ruins. 

Nothing  could  at  first  be  found  of  the  engineer.  Par- 
ties searched  for  long  distances  about  the  wreck  for  signs 
of  the  unfortunate  man,  but  it  was  not  until  next  morn- 
ing that  his  body  was  found.  It  was  discovered  lying  in 
the  woods,  seven  hundred  feet  away  from  the  locomo- 
tive, which  was  completely  demolished,  and  every 
part  of  the  machinery  was  twisted  or  broken  into  pieces. 


1 4o  STEAM  BOILER  EXPLOSIONS. 

The  track  was  torn  up  for  some  distance,  and  rails  were 
bent  like  coils  of  rope. 

The  fire-box  of  the  locomotive  was  hurled  from  its 
position  and  broken  into  many  pieces.  A  large  piece, 
weighing  many  hundred  pounds,  was  carried  500  feet 
The  dome  and  sand-box  were  thrown  an  eighth  of  a  mile 
into  the  adjacent  river.  The  wheels  of  the  engine  were 
torn  off,  and  not  one  piece  of  the  cab  was  discovered. 
The  engineer  bore  an  excellent  reputation  as  being  a 
careful  man,  always  carrying  a  large  supply  of  water. 
The  engine  was  one  of  approved  make,  and  been  in  use 
for  fifteen  years.  It  had  just  come  from  the  repair  shop. 
A  new  fire-box  had  been  put  in  three  years  before,  and 
the  boiler  was  thoroughly  examined  about  six  weeks 
earlier.  The  iron  was,  in  many  cases,  twisted  and  bent 
into  shapeless  rolls.  The  point  of  rupture  was  appar- 
ently in  the  left  hand  lower  corner  of  the  outside  shell  of 
the  fire-box.  The  cause  was  variously  assigned  as  a 
percussive  or  " fulminating"  action  due  to  over-heated 
iron  and  to  certain  defective  portions  of  the  fire-box. 
The  latter  was  probably  the  true  cause. 

The  following  may  be  taken  as  another  illustration 
of  the  tremendous  effects  of  explosion  at  usual  work- 
ing pressure  with  an  ample  supply  of  water.  A  boiler 
of  the  locomotive  type  was  constructed  for  use  in  a  small 
steamer.  Its  shell  was  of  iron,  4  feet  in  diameter  and 
5-i6th-inch  thick.  It  was  "tested"  by  filling  with 
water  and  raising  steam.  It  exploded  with  the  safety- 
valve  set  at  1 20  pounds  per  square  inch,  blowing  freely 
although  held  down  by  the  man  in  charge,  and  killed 


THE  RESULTS  OF  EXPLOSIONS.  141 

and  injured  several  people.  The  hiss  of  steam  es- 
caping from  the  initial  rupture  was  heard  an  instant  be- 
fore the  explosion.  The  boiler  was  turned  end  for  end, 
and  the  fire-box  torn  from  the  boiler  in  two  pieces,  one 
being  carried  to  a  distance  of  about  five  hundred  feet  and 
imbedded  in  the  mud  of  a  canal  bed;  the  other  portion, 
weighing  about  4,800  pounds,  was  carried  a  distance  of 
between  400  and  500  feet,  and  crashed  into  the  side  of 
a  building,  and  with  sash,  blinds  and  doors,  piled  closely 
together.  One  piece  of  iron  comprised  the  fire-box, 
the  dome,  and  the  end  of  the  boiler,  and  was  straightened 
into  a  piece  30  feet  long  and  four  feet  wide.  The  piece  is 
said  to  have  rushed  through  the  air  with  a  whirling  motion 
until  it  struck  the  building.  It  cut  the  side  of  the  build- 
ing and  beams  and  rafters  like  straws,  pushing  the  front 
of  the  building  forward  several  feet.  Fragments  of  the 
boiler  were  found  at  many  points  considerably  distant 
from  the  scene  of  the  explosion,  and  in  many  places  win- 
dows were  shattered  by  the  concussion. 

The  shell  of  the  boiler  was  reversed  by  the  force  of  the 
explosion,  with  such  force  that  one  end  was  buried  four 
feet  in  the  road  bed.  All  the  flues  remained  in  the  boiler, 
one  end  of  which  was  torn  from  them  while  the  other  re- 
mained in  place. 

At  the  instant  of  the  explosion  the  air  for  many  feet 
in  every  direction  was  filled  with  flying  fragments,  many 
of  them  being  thrown  to  a  great  height. 

In  one  case  coming  under  the  observation  of  the 
Author,  a  locomotive  set  as  a  stationary  boiler  gave  way 
in  the  fire-box,  and  let  out  the  water  and  steam,  but  in- 


142  STEAM  BOILER  EXPLOSIONS. 

j tiring  no  one.  The  rent  was  about  twelve  inches  long 
and  eight  inches  wide.  The  iron  in  that  place  was  weak- 
ened by  corrosion,  otherwise  the  boiler  was  in  good  con- 
dition. Repairs  were  immediately  commenced  and  the 
boiler  was  ready  for  use  next  day.  Had  this  rent  oc- 
curred at  or  above  the  water-level,  it  is  very  possible  that 
an  explosion  may  have  resulted  in  the  manner  suggested 
by  Clark  and  Colburn. 

In  an  explosion  of  a  tubular  boiler  at  Dayton,  O., 
October  25th,  1881,*  by  which  several  lives  and  much 
property  were  destroyed,  the  rupture  started  along  the 
lap  A  B  in  the  figure,  and  was  evidently  due  to  the 


FIG.  43. — INITIAL  RUPTURE  ;    "  GROOVING." 

furrowing  which  had  been  there,  in  some  way,  produced. 
The  boiler  was  less  than  a  year  old,  and  was  reported 
to  be  of  good  material  and  workmanship.  The  longi- 
tudinal seams  were  double-riveted,  and  it  is  very  possi- 
ble that  the  stiffness  thus  produced  along  their  lines 
may  have  so  localized  the  strains  due  to  alterations  of 

*  Scientific  American,  Dec.  iyth,  1881. 


THE  RESULTS   OF  EXPLOSIONS.  143 

form  as  to  have  led  to  this  fatal  result,  aided  by  the 
action  of  the  caulking  tool,  the  marks  of  which,  along 
the  lines  at  which  the  crack  gradually  worked  through 


FIG.  44. — BOILER  EXPLOSION  AT  DAYTON, 
OHIO. 

the  sheet,  are  plainly  visible.  The  boiler  had,  when 
first  set  in  place,  been,  tested  to  140  pounds;  the  explo- 
sion occurred  at  probably  less  than  80. 


FIG.  45. — GIRDLE  OF  PLATES 
FROM  No.  2  BOILER. 


A  strip  of  plates,  as  in  the  above  figure,  was  torn 
from  the  boiler,  separating  it  into  two  parts,  as  seen  in 


144 


STEAM  BOILER  EXPLOSIONS. 


FIG.  46. — REAR  END  OF  BOILER  AFTER  EX- 
PLOSION. REAR  END  OF  BOILER  BEFORE 
EXPLOSION. 

the  two  succeeding  figures,  and  throwing   them  apart 


FIG.  47. — FRONT  END  OF  BOILER 
AFTER  EXPLOSION. 

with  all  the  force  due  to  a  hundred  millions  of  foot- 


5.— Principal  part  of  No.  5  boiler  thrown  over  the  church  on  the  bluff. 
6. — Principal  part  of  No.  6  boiler. 

FIG.  48. — EXPLOSION  OF  TWO  STEAM  BOILERS  AT  PITTSBURG,  PA. 


THE  RESULTS  OF  EXPLOSIONS.  I45 

pounds  of  available  stored  heat-energy,  entirely    de- 
stroying the  house  in  which  they  were  set. 

In  a  case  of  explosion  at  Pittsburg,  Pa.,  in  December, 
1 88 1,  a  battery  of  flue-boilers  was  connected,  as  seen  in 
the  figure,  by  steam-drums  above  the  nearer  two  and 


FIG.  49. — UNDER  SIDES  OF  BOILERS. 

mud-drums  beneath  all  three.  The  steam-pressure  was 
not  far  from  125  pounds  per  square  inch  at  the  time  of 
the  accident  The  boilers  were  fifteen  years  old,  but 
had  been  tested  to  1 70  pounds  two  years  earlier,  and 
allowed  to  work  at  120  pounds,  although  they  had  been 
repeatedly  patched  and  repaired.*  The  rules  of  the 
insurance  companies  would  have  allowed  but  one-half 
this  pressure. 

The  strains  produced  by  the  changes  of  form  with 
varying  temperature  of  feed- water,  and  by  the  action 
of  the  new  iron  of  the  patches  on  the  older  and  corroded 
parts  of  the  boilers,  started  cracks  which  gradually 
weakened  them,  and  finally  led  to  a  rupture  along  the 
worst  line  of  injury,  A  By  in  the  preceding  figure,  open- 
ing the  course  of  plates  at  a,  and  tearing  it  out  as  in 

*  Scientific  American,  Feb.  4,  1882. 


1 40 


STEAM  BOILER  EXPLOSIONS. 


the  next  figure,  in  which  A  B  is  the  line  of  initial  frac- 
ture. The  destruction  of  this  (No.  6)  boiler  was  accom- 
panied by  the  disruption  of  that  next  to  it  (No.  5), 
which  was  also  in  about  as  dangerous  condition.  The 
available  energy  of  the  explosion  was  about  250,000,000 


FIG.  50. — COURSE  OF  PLATES  DETACHED. 

foot-pounds,  and  the  damage  produced  was  proportioned 
to  this  enormous  power. 

One  boiler  (No.  5)  was  thrown  across  the  road  and 
over  a  church  ;  the  other  (No.  6)  was  thrown  to  one 


FIG.  51.— PIECE  OF  "  PATCH." 

side,  partially  destroying  neighboring  buildings.  The 
boiler-house  was  entirely  destroyed.  The  third  boiler 
remained  unexploded  and  was  found  a  little  out  of  place 
and  nearly  full  of  water. 


THE   RESULTS   OF  EXPLOSIONS. 


147 


According  to  the  observer  furnishing  these  particulars, 
the  conclusions  are  inevitable : 

That  the  two  boilers  exploded  in  succession  so  quickly 
as  to  be  practically  simultaneous,  beginning  at  the  weak 
line  A  B  of  No.  6  boiler ; 

That  they  contained  an  ample  supply  of  water ; 

That  the  pressure  was  too  great  for  boilers  of  their 
size  and  condition. 

That  the  use  of  cold  feed-water  hastened  the  deterio- 
ration of  poor  iron,  causing  cracks  and  leaks,  by  which 
external  corrosion  was  produced,  and  that  the  energy 
stored  in  the  water  of  these  boilers  caused  all  the 
destruction  observed. 

It  is  always  to  be  strongly  recommended  that  regular 
and  continuous  feeding  of  hot  water  be  practiced;  and 
that  the  greatest  care  be  exercised  by  inspectors  and 
those  in  charge  of  steam-boilers  in  searching  for  and 
immediately  repairing  dangerous  defects. 

The  last  figure,  preceding,  is  an  excellent  illustration 
of  the  appearance  of  iron  when  thus  corroded.  At  C, 
the  crack  was  old  and  partly  filled  up  with  lime  scale. 

The  explosion  of  the  upright  tubular- boiler  is  usually 
consequent  upon  some  injury  of  its  furnace,  either  by 
collapse  or  by  the  yielding  of  the  tube-sheet  to  exces- 
sive pressure.  The  result  is  commonly  the  projection 
of  the  boiler  upward  like  a  rocket,  and  is  rarely  accom- 
panied by  much  destruction  of  property  laterally.  A 
typical  case  of  this  kind  is  that  of  an  explosion  occur- 
ring at  Norwich,  Connecticut,  December  23,  1881,  of 
which  the  following  is  a  brief  account:* 

*  Scientific  American,  Jan.  14,  1882 


148 


STEAM  BOILER  EXPLOSIONS. 


FIG,  52. — EXPLOSION  OF  AN  UPRIGHT  BOILER. 

Fig.  53  represents  the  location  of  the  boiler  and 
engine  immediately  before  the  explosion.  The  explo- 
sion took  place,  as  shown  in  figure  by  the  yielding  of 
the  lower  tube  plate  of  the  boiler. 

This  boiler  was  three  feet  in  diameter  and  seven  feet 
high.  The  boiler  was  made  of  five-sixteenths  iron 
throughout.  It  contained  sixty  tubes,  two  inches  diam- 
eter, five  feet  long,  which  were  set  with  a  Prosser  ex- 
pander, and  were  beaded  over  as  usual.  The  upper  tube- 
head  was  flush  with  the  top  of  the  shell,  and  the  lower, 
forming  the  crown  of  the  furnace,  was  about  two  feet 
above  the  grates  and  the  base  of  the  shell,  and  was  flanged 
upon  the  inner  surface  of  the  furnace.  There  was  a 
safety  plug  in  the  lower  tube-head,  which  was  not  melted 
out,  although,  as  is  often  the  case  when  these  plugs  are 


THE   RESULTS   OF  EXPLOSIONS. 


149 


so  near  the  fire,  a  portion  of  the  lower  part  of  the  fusible 
filling  had  disappeared. 


"  •  .i^UNiHtfa^j^F*-- 
FIG.  53. — THE  BOILER  ROOM  BEFORE  THE  EXPLOSION. 

The  working  pressure  was   sixty  pounds  per  square 
inch,  and  the  explosion  probably  took  place  at  or  a  little 


FIG.  54. — YIELDING  TUBE  SHEFT: 

below  this  pressure,  throwing  the  boiler  through  the  roof 
and  high  over  a  group  of  buildings  and  a  tall  tree  close 


STEAM  BOILER  EXPLOSIONS, 


by,  finally  burying  itself  half  its  diameter  in  the  frozen 
ground. 


FIG.  55. — THE  EXPLODED  BOILER. 

There  had  been  leaks  in  the  tubes  and  four  had  been 
plugged.  There  was  a  crack  in  the  upper  head  near  the 
center  which  extended  between  three  tubes.  From  this 
crack  steam  escaped,  and  the  water  had  settled  upon  the 
surrounding  surface  of  the  tube-head  and  the  tube-ends. 
The  result  was  to  reduce  the  five-sixteenths  plate  to  less 
than  a  quarter  of  an  inch  in  thickness,  and  the  tube-ends 
to  the  thickness  of  writing  paper.  The  lower  tube-ends 
had  suffered  still  more  from  leaks  and  were  as  thin  as  paper 
and  afforded  no  adequate  support  to  the  head.  The 
pressure  consequently  forced  the  lower  head  down,  open- 
ing fifty  or  more  holes,  two  inches  diameter,  from  which 
the  fluid  contents  of  the  boiler  issued  at  a  high  velocity, 
and  the  whole  boiler  became  a  great  rocket  weighing 
about  two  thousand  pounds. 


THE  RESULTS   OF  EXPLOSIONS.  151 

One  life  was  destroyed  by  this  explosion  and  a  con- 
siderable amount  of  property. 

An  explosion  which  occurred  at  Jersey  City,  N.  J., 
some  years  ago,  illustrated  at  once  the  dangers  of  low- 
water  and  of  a  safety-valve  rusted  fast.  As  reported  at 
the  time:*  "The  boiler  was  of  the  locomotive  type; 
having  a  dome  upon  the  top.  The  engineer  upon  the 


FIG.  56. — THE  EXPLOSION. 

morning  of  the  explosion  lighted  the  fire  in  the  boiler 
and  shortly  afterward  was  called  away,  leaving  the  boiler 
in  charge  of  his  nephew,  who  was  young  and  inexperienced 
in  the  handling  of  steam.  After  putting  fresh  coal  in 
the  furnace  he  was  called  away  by  one  of  the  owners  of 
the  dock  to  assist  at  some  outside  duty.  Upon  his  re- 


*Am.  Machinist,  Oct.  ist,  1881. 


It; 2  STEAM  BOILER  EXPLOSIONS. 

turn  he  saw  the  seams  of  the  boiler  opening,  and  attempted 
to  open  the  furnace  door,  but  was  unable,  owing  to  the 
excess  of  pressure  of  steam  within  the  boiler  which  had 
caused  the  head  to  change  its  shape.  A  few  moments 
afterward  the  explosion  occurred.  The  fire-box  being 
thrown  downward,  the  top  of  the  shell  and  crown-sheet 
upward,  while  the  cylinder  part  shot  directly  up  the 
street.  It  struck  the  ground  about  400  feet  from  its 
original  position,  demolished  afire  hydrant,  several  trucks, 
trees,  and  a  horse,  and,  spinning  end  for  end,  came  to 
rest  by  the  side  of  a  truck,  which  it  destroyed,  about 
642  feet  from  its  starting  point.  Subsequent  investiga- 
tion revealed  the  fact  that  the  boiler  was  not  properly 
supplied  with  water.  A  portion  of  the  crown  sheet 
which  we  examined  showed  conclusively  that  near  the 
flues  it  was  red-hot.  We  also  examined  the  safety- valve, 
which  was  of  the  wing  pattern,  having  a  lever  and  weight. 
This  valve  was  so  firmly  corroded  to  its  seat  that  it  could 
not  be  removed,  and  the  stem  was  also  corroded  fast. 
The  whole  secret  of  this  explosion  is  that  the  boiler  was 
short  of  water  and  an  excessively  high  pressure  of  steam 
was  raised  to  an  unknown  point ;  which,  without  relief, 
acquiring  sufficient  force,  tore  the  boiler  to  pieces." 

The  valve  was  found  and,  being  placed  in  a  testing 
machine  then  under  the  charge  of  the  Author,  at  the 
Stevens  Institute  of  Technology,  was  only  started  by  a 
pressure  of  a  ton  and  a  half;  *  while  nearly  two  tons 
was  required  to  move  it  observably. 

*Ibid,  Oct.  22d,  1881. 


THE  RESULTS  OF  EXPLOSIONS. 


'53 


Change  of  form  with  varying  pressures  and  tempera- 
tures sometimes  produces  most  unexpected  defects.     It 


FIG.  57. — FAULTY  STAYING. 

has  been  observed  that  many  locomotive  boilers  stayed 
as  in  the  figure,  *  give  way  at  the  side,  in  the  manner 
here  exhibited.  Investigation  shows  that,  in  these  cases, 
the  tying  of  the  furnace-crowns  to  the  shell  by  the  sys- 
tem of  staying  illustrated,  and  the  continual  rising  and 
falling  of  the  furnace  relatively  to  the  shell,  is  very  apt  to 
cause  a  buckling  of  the  outside  sheet  along  the  horizontal 
seam,  which  finally  yields.  This  buckling  and  straight- 
ening of  the  sheet  goes  on  until  a  crack  or  a  furrow  is 
formed  along  the  lap  nearest  the  most  rigid  brace,  and, 
when  this  has  cut  deeply  enough,  the  side  of  the  boiler 
opens,  often  the  whole  length  of  the  furnace,  the  ex- 
plosion doing  an  amount  of  damage  which  is  determined 

*  Locomotive,  Jan.  I,  1880. 


I54  STEAM  BOILER  EXPLOSIONS. 

by  the  steam  pressure,  the  quantity  of  energy  stored,  and 
the  extent  of  the  rupture. 


FIG.  58. — COLLAPSED  FLUES. 

In  these  cases,  either  the  crown-bars  over  the  furnace, 
or  the  stays,  should  alone  have  been  used  ;  their  use  to- 


FIG.  59. — COLLAPSED  FLUES. 

gether  is  objectionable.      Of  the  two  systems,  probably 
the  first  is  safest  in  such  boilers. 

The  appearance  of  a  collapsed  flue  is  seen  in  the  two 


THE  RESULTS  OF  EXPLOSIONS.  155 

succeeding  figures,  which  represent  the  results  of  experi- 
ments made  by  the  U.  S.  Commission  appointed  to 
investigate  the  causes  of  explosions  of  steam  boilers. 
In  neither  case  did  the  boiler  move  far  from  its  original 
position.  Collapsed  flues  rarely  cause  extensive  destruc- 
tion of  property. 

An  explosion  of  a  rotary  rag-boiler,  receiving  steam 
from  steam-boilers  at  a  distance,  which  took  place  at 
Paterson,  N.  J.,  wrecked  the  mill,  destroyed  a  part  of 
an  adjacent  establishment,  and  caused  serious  loss  of 
life  and  property.  The  disaster  was  due  to  the  weak- 
ening of  the  boiler  by  corrosion,  but,  notwithstanding 
its  reduced  strength,  the  shock  of  the  explosion  was 
felt,  and  was  heard,  throughout  the  city,  and  heavy 
plate- glass  windows  were  broken  at  a  considerable  dis- 
tance from  the  scene  of  the  accident.  Explosions  of 
this  kind  show  the  fallacy  of  many  of  the  absurd  and 
mischievous  "  theories"  which  have  been  prevalent  in 
regard  to  explosions. 

Where  the  iron  or  steel  used  in  the  construction  of  the 
boiler  is  of  good  quality,  strong,  uniform  and  ductile, 
the  smaller  torn  parts  of  an  exploded  boiler  may  not 
break  away  from  the  main  body ;  such  a  case  is  illus- 
trated in  the  accompanying  figure,  which  represents  the 
effect  of  an  explosion  of  a  new  boiler  from  a  cause  not 
ascertained. 

The  boiler  was  1 5  feet  long  by  4  feet  diameter,  with 
38  four-inch  flues.  Both  heads  remained  on  the  flues, 
but  the  shell  of  the  boiler  burst  along  the  rivet- holes 
nearly  all  around  both  heads,  as  shown  in  the  engraving. 


156  STEAM  BOILER  EXPLOSIONS. 

32.  Experimental  Investigations  of  the  causes  and 
methods  of  steam-boiler  explosions  have  been  occasion- 
ally attempted.  One  of  the  earliest  and  most  syste- 


FIG.  60. — AN  EXPLODED  BOILER. 

matic,  as  well  as  fruitful,  was  that  of  a  Committee  of  the 
Franklin  Institute,  the  results  of  which  were  reported  to 
the  Secretary  of  the  U.  S.  Treasury,  early  in  1836. 

Unpublished  experiments  recently  made  by  Professor 
Mason  at  the  Rensselaer  Polytechnic  Institute,  strongly 
confirm  the  so-called  "  geyser  theory"  of  Messrs.  Clark 
and  Colburn.  In  these  experiments  a  number  of  mina- 
ture  boilers  were  constructed,  and  were  exploded  by  a 
gradually  produced  excess  of  pressure,  and  in  such 
manner  as  to  test  this  theory.  The  first  of  these  boilers, 
when  exploded,  produced  such  an  effect,  blowing  out 
windows  and  shaking  down  the  ceiling  of  the  laboratory 
as  effectually  to  dispose  of  the  idea  prevalent  among 
certain  classes  of  engineers,  that  a  true  explosion  could 
only  be  caused  by  low-water  and  overheated  plates. 
Another  boiler  was  so  set  that,  the  rear  end  being  lower 
than  the  front,  the  quantity  of  water  acting  by  percus- 


EXPERIMENTAL  INVESTIGA  TIONS. 


157 


sion,  according  to  the  Clark  theory,  was  much  greater 
at  the  one  end  than  at  the  other.  The  consequence  was 
that,  while  the  one  end  was  broken  into  many  pieces, 
that  in  which  there  was  least  water  was  simply  torn 
from  the  mass  of  the  boiler  and  was  itself  unbroken. 
In  one  of  this  series  of  experiments  the  boiler  was 
broken  into  more  than  a  hundred  pieces,  although 
made  of  drawn  brass,  a  material  far  less  liable,  ordina- 
rily, to  be  thus  shattered  than  iron  or  steel.  The  second 
of  the  above  described  experiments  appears  to  the 
Author  a  very  nearly  crucial  test  and  proof  of  the 
theory  of  Messrs.  Clark  and  Colburn. 

The  Franklin  Institute  committee  proposed  by  ex- 
periments : 

(I).  To  ascertain  whether,  on  relieving  water  heated 
to,  or  above,  the  boiling  point,  from  pressure,  any  com- 
motion is  produced  in  the  fluid. 

To  determine  the  value  of  glass  gauges  and  gauge- 
cocks. 

The  investigation  of  the  question  whether  the  elasti- 
city of  steam  within  a  boiler  may  be  increased  by  the 
projection  of  foam  upon  the  heated  sides,  more  than  it 
is  diminished  by  the  openings  made. 

(II).  To  repeat  the  experiments  of  Klaproth  on  the 
conversion  of  water  into  steam  by  highly  heated  metal 
and  to  make  others,  calculated  to  show  whether,  under 
any  other  circumstances,  intensely  heated  metal  can 
produce,  suddenly,  great  quantities  of  highly  elastic 
steam. 

To  directly  experiment  in  relation  to  the  production 


158  S TEA M  B OILER  EXPLOSIONS. 

of  highly  elastic  steam  in  a  boiler  heated  to  high  temper- 
ature. 

(III).  To  ascertain  whether  intensely  heated  and  un- 
saturated  steam  can,  by  the  projection  of  water  into  it, 
produce  highly  elastic  vapor. 

(IV).  When  the  steam  surcharged  with  heat  is  pro- 
duced in  a  boiler,  and  is  in  contact  with  water,  does  it 
remain  surcharged,  or  change  its  density  and  tempera- 
ture ? 

(V).  To  test,  by  experiment,  the  efficacy  of  plates, 
etc.,  of  fusible  metal,  as  a  means  of  preventing  the  undue 
heating  of  a  boiler,  or  its  contents. 

(i).   Ordinary  fusible  plates  and  plugs. 

(2).   Fusible  metal,  inclosed  in  tubes. 

(3).  Tables  of  the  fusing  points  of  certain  alloys. 

(VI).  To  repeat  the  experiments  of  Klaproth,  &c. 

(i).  Temperature  of  maximum  vaporization  of  copper 
and  iron  under  different  circumstances. 

(2).  The  extension  to  practice,  by  the  introduction  of 
different  quantities  of  water,  under  different  circum- 
stances of  the  metals. 

(VII).  To  determine  by  actual  experiment,  whether 
any  permanently  elastic  fluids  are  produced  within  a 
boiler  when  the  metal  becomes  intensely  heated. 

(VIII).  To  observe  accurately  the  sort  of  bursting 
produced  by  a  gradual  increase  of  pressure,  with  cylin- 
ders of  iron  and  copper. 

(IX).  To  repeat  Perkins'  experiment  and  ascertain 
whether  the  repulsion  stated  by  him  to  exist  between 
the  particles  of  intensely  heated  iron  and  steam  be  gen- 


EXPERIMENTAL   INVESTIGATIONS.  159 

eral,  and  to  measure,  if  possible,  the  extent  of  this  re- 
pulsion, with  a  view  to  determine  the  influence  it  may 
have  on  safety-valves. 

(X).  To  ascertain  whether  cases  may  really  occur 
when  the  safety-valve,  loaded  with  a  certain  weight,  re- 
mains stationary,  while  the  confined  steam  acquires  a 
higher  elastic  force  than  that  which  would,  from  calcu- 
lation, appear  necessary  to  overcome  the  weight  of  the 
valves. 

(XI).  To  ascertain  by  experiment  the  effects  of  de- 
posits in  boilers. 

(XII).  Investigation  of  the  relation  of  temperature  and 
pressure  of  steam,  at  ordinary  working  pressures. 

It  is  only  necessary  here  to  state  that  the  result 
proved : 

(i).  That  relieving  pressure,  even  slightly,  produced 
great  commotion  in  the  water,  and  considerably  reliev- 
ing it  caused  the  violent  ejection  of  water  as  well  as 
steam  through  the  opening  by  which  the  pressure  was 
reduced. 

(2).  That  under  similar  conditions  pressure  invariably 
diminished. 

(3).  That  the  injection  of  water  upon  the  heated  sur- 
faces of  the  experimental  boiler,  produced  a  sudden  and 
considerable  rise  of  pressure. 

(4).  That  the  injection  of  water  into  superheated  steam 
reduced  its  pressure. 

(5).  That  superheated  steam  may  remain  in  contact 
with  water  a  long  time  (two  hours  in  the  experiments 
tried),  without  becoming  saturated. 


!6o  STEAM  BOILER  EXPLOSIONS. 

(6).  That  fusible  plugs,  as  then  constructed,  were  un- 
reliable. The  fusing  point  of  various  alloys  were  de- 
termined. 

(7).  That  the  temperature  of  maximum  vaporization 
of  water  is  lowered  by  smoothness  of  surfaces ;  that  that 
of  iron  is  thirty  or  forty  degrees  higher  than  that  of  cop- 
per, while  the  time  required  is  one-half  as  great  with 
copper;  that  the  temperature  of  maximum  vaporization, 
for  oxidized  iron,  or  for  highly  oxidized  copper  is  about 
350°  F.,  and  that  the  repulsion  between  the  metal  and 
the  water  is  perfect  at  from  twenty  to  forty  degrees  above 
the  temperature  of  maximum  vaporization. 

(8).  That  no  hydrogen  is  liberated  by  throwing  water 
or  steam  upon  heated  surfaces  of  the  boiler;  that 
the  water  was  not  decomposed,  and  that  air  cannot  oc- 
cur in  any  appreciable  quantity  in  a  steam-boiler  at  work. 

(9).  That  "all  the  circumstances  attending  the  most 
violent  explosions  may  occur  without  a  sudden  increase  of 
pressure  within  a  boiler"  the  explosion  being  produced 
by  gradually  accumulated  pressure. 

(10).  That  but  a  small  portion  of  water,  highly  heated, 
can  expand  into  steam,  if  suddenly  relieved  of  pressure. 

(i  i).  That  water  can  be  heated  to  very  high  temper- 
ature only  under  immensely  high  pressure. 

(12).  That  steam-pressure  may  rise  even  after  it  has 
raised  the  safety-valve. 

Over  thirty  years  passed  before  another  serious  at- 
tempt was  made  to  thoroughly  investigate  the  subject,* 


EX  PERI  MEN  TAL  IX  VE  S  TIG  A  TIONS.  1 6 1 

but  in  the  year  1871,  experiments  were  inaugurated  on  a 
large  scale.* 

In  the  work  of  investigation  involving  the  explosion 
of  steam-boilers,  it  is  usually  necessary  to  provide  a  safe 
retreat  for  the  observers,  from  which  to  watch  the  pro- 
gress of  the  experiment,  and  from  which  to  read  the 
steam-gauge,  to  watch  the  water-level,  and  to  take  the 
reading  of  the  thermometers  or  pyrometers. 


FIG.    61. — BOMB-PROOF. 

The  illustration  represents  the  structure,  composed  of 
heavy  timber,  and  partially  underground,  used  at  the 
testing  ground  at  Sandy  Hook,  by  the  U.  S.  Commis- 
sion of  1873-6. 

These  experiments  were  projected  and  conducted  by 
Mr.  Francis  B.  Stevens,  of  Hoboken,  and  at  the  request  of 
Mr.  S.  the  United  Railroad  Companies  of  New  Jersey 
appropriated  the  sum  of  ten  thousand  dollars  to  enable 
Mr.  Stevens  to  enter  upon  a  preliminary  series  of  ex- 

*  Journal  Franklin  Inst.,  Jan.,  1872. 


!62  STEAM  BOILER  EXPLOSIONS. 

periments.  They,  at  the  same  time,  invited  other  rail- 
roads and  owners  of  steam-boilers  to  co-operate  with 
them,  and  offered  the  use  of  their  shops  for  any  work 
that  might  be  considered  necessary  or  desirable  during 
the  progress  of  the  work ;  no  such  aid  was,  however,  re- 
ceived. 

Several  old  boilers  had  recently  been  taken  out  of  the 
steamers  of  the  United  Companies.  These  were  sub- 
jected to  hydrostatic  pressure,  until  rupture  occurred, 
were  repaired  and  again  ruptured  several  times  each,  thus 
detecting  and  strengthening  their  weakest  spots,  and 
finally  leaving  them  much  stronger  than  when  taken  from 
the  boats.  The  points  at  which  fracture  occurred  and 
the  character  of  the  break  were  noted  carefully  at  each 
trial. 

After  the  weak  spots  had  thus  been  felt  out  and 
strengthened,  the  boilers  were  taken,  with  the  permis- 
sion of  the  War  Department,  to  the  U.  S.  reservation  at 
Sandy  Hook,  at  the  entrance  to  New  York  Harbor,  and 
were  there  set  up  in  a  large  enclosure  which  had  been  pre- 
pared to  receive  them,  and  the  four  old  steamboat  boilers 
above  referred  to,  together  with  five  new  boilers  built  for 
the  occasion,  were  placed  in  their  respective  positions 
without  having  been  in  any  way  injured. 

Finally,  on  the  22d  and  23d  of  November,  the  exper- 
iments to  be  described  were  made. 

The  first  boiler  attacked  was  an  ordinary  "  single  return 
flue  boiler." 

The  cylindrical  portion  of  the  shell  was  6  feet  6  inches 
diameter,  20  feet  4  inches  long,  and  of  iron  a  full  quarter 


EXPERIMENTAL  INVESTIGATIONS. 


FIG.  62.— MARINE  BOILER.  " 

inch  thick.  The  total  length  of  the  boiler  was  28  feet, 
the  steam  chimney  was  4  feet  diameter,  10^  feet  high^ 
and  its  flue  was  32  inches  diameter.  The  two  furnaces 
were  7  feet  long,  with  flat  arches.  There  were  ten 
lower  flues,  two  of  16  and  eight  of  9  inches  diameter, 
and  all  were  1 5  feet  9  inches  long ;  there  were  twelve 
upper  flues,  8^  inches  in  diameter,  and  22  feet  long. 
The  total  grate  surface  was  38^  square  feet,  heating  sur- 
face 1350  square  feet.  The  water  spaces  were  4  inches 
wide,  and  the  flat  surfaces  were  stayed  by  screw  stay- 
bolts  at  intervals  of  7  inches.  The  boiler  was  thirteen 
years  old,  and  had  been  allowed  40  pounds  pressure. 

The  upper  portion  of  the  boiler,  when  inspected  before 
the  experiment,  seemed  to  be  in  good  order.     The  girth 


164 


STEAM  BOILER  EXPLOSIONS. 


seams  on  the  under  side  of  the  cylindrical  portion  had 
given  way,  and  had  all  been  patched  before  it  was  taken 
out  of  the  boat  The  water  legs  had  been  considerably 
corroded. 

In  September  this  boiler  had  been  subjected  to  hy- 
drostatic pressure,  giving  way  by  the  pulling  through 
of  stay-bolts  at  66  pounds  per  square  inch.  It  was  re- 
paired and,  afterward,  at  Sandy  Hook,  was  tested  without 
fracture  to  82  pounds,  and  still  later  bore  a  steam  pres- 
sure of  60  pounds  per  square  inch. 

On  its  final  trial,  Nov.  22d,  a  heavy  wood  fire  was 
built  in  the  furnaces,  the  water  standing  1 2  inches  deep 
over  the  flues,  and,  when  steam  began  to  rise  above  50 
pounds,  the  whole  party  retired  to  the  gauges,  which  were 
placed  about  250  feet  from  the  enclosure.  The  notes  of 
pressures  and  times  were  taken  as  follows : 


Time.       Pressure. 

Time.       Pressure. 

Time.       Pressure. 

Time.       Pressure. 

2.ooP.M.     58  Ibs. 
2.05     "         68     " 
2.10    "         78     " 

2.15  P.M.     87    Ibs. 

2.20      "              9I^    " 

2.23      '          93 

2.25  P.M.    91^  Ibs. 

2'36     ,',         9I17  » 
2-35               91A 

2.40  P.M.     91%  Ibs. 

2-45     "          91      ' 
2.50     "          90      ' 

The  pressure  rose  rapidly  until  it  reached  about  90 
pounds,*  when  leaks  began  to  appear  in  all  parts  of  the 
boiler,  and  at  93  pounds  a  rent  at  A,  (Fig.  62)  the  lower 
part  of  the  steam  chimney  where  it  joins  the  shell  becom- 
ing quite  considerable,  and  other  leaks  of  less  extent  en- 

*  The  ultimate  strength  of  this  boiler,  when  new,  was  probably  equal 
to  about  double  this  pressure. 


EXPERIMEN TA L  IN  VESTIGA  TIONS. 


165 


larging,  the  steam  passed  off  more  rapidly  than  it  was 
formed.  The  pressure  then  slowly  diminishing,  the 
workmen  extinguished  the  fires  by  throwing  earth  upon 
them,  and  the  experiment  thus  ended. 

The  second  experiment  was  made  with  a  small  boiler 


* 


FIG.  63. — STAYED  WATER  SPACE. 

(Figure  63)  which  had  been  constructed  to  determine 
the  probable  strength  of  the  stayed-surface  of  a  marine 
boiler.  It  had  the  form  of  a  square  box,  6  feet  long,  4 
feet  high,  and  4  inches  thick.  Its  sides  were  6  inch 
thick,  of  the  "best  flange  fire-box"  iron.  The  water- 
space  was  3  j£  inches  wide.  The  rivets  along  the  edges 
were  ^  inch  diameter,  spaced  2  inches  apart.  The  two 
sides  were  held  tegether  by  screw  stay-bolts,  spaced  8  ^ 
and  9^  inches,  and  their  ends  were  slightly  riveted 
over,  precisely  copying  the  distribution  and  workman- 
ship of  a  water-leg  of  an  ordinary  marine  boiler  It  had 
been  tested  to  138  Ibs.  pressure.  This  slab  was  set  in 
brickwork,  about  five-sixths  of  its  capacity  occupied  by 
water,  and  fires  built  on  both  sides.  Pressure  rose  as 
shown  by  the  following  extract  from  the  note-book  of 
the  Author : 


i66 


STEAM  BOrLER  EXPLOSIONS. 


Time.      Pressure. 

Time.     Pressure. 

Time.     Pressure. 

Time.       Pressure 

3.18  P.M.      o  Ibs. 

3.27  P.M.       18  Ibs. 

3.35  P.M.      49  Ibs. 

3.43  P.  M.      94  Ib 

3.20 

4 

3.28        '                 20      k' 

3-36 

Si 

3-44                 *°o 

3.21 
3.22 

5 
7 

3-29       '                23       *' 
3.30       *                27 

3-37 
3.38 

3 

3-45 
3.46 

HO 

117 

3-23 

9 

3-31            30  '; 

3-39 

65 

3-47      ' 

126 

S.24 

ii 

3-32     '            34 

3-40 

72 

3-48      ' 

*35 

3.25 

13 

3-33                  38 

3-4i 

£ 

3-49      ' 

147 

3-26 

15 

3-34                  44 

3-42 

86 

3-50 

160 

3-51 

16°; 

Exploded. 

At  a  pressure  of  slightly  above  165,  and  probably  at 
about  167  pounds,  a  violent  explosion  took  place. 
The  brickwork  of  the  furnace  was  thrown  in  every 
direction,  a  portion  of  it  rising  high  in  the  air  and  fall- 
ing among  the  spectators  near  the  gauges ;  the  sides  of 
the  exploded  vessel  were  thrown  in  opposite  directions 
with  immense  force,  one  of  them  tearing  down  the  high 
fence  at  one  side  of  the  enclosure,  and  falling  at  a  con- 
siderable distance  away  in  the  adjacent  field ;  the  other 
part  struck  one  of  the  large  boilers  near  it,  cutting  a 
large  hole,  and  thence  glanced  off,  falling  a  short  dis- 
tance beyond. 

Both  sides  were  stretched  very  considerably,  assum- 
ing a  dished  form  of  8  or  9  inches  depth,  and  all  of  the 
stay-bolts  drew  out  of  the  sheets  without  fracture  and 
without  stripping  the  thread  of  either  the  external  or  the 
internal  screw;  this  effect  was  due  partly  to  the  great 
extension  of  the  metal^  which  enlarged  the  holes,  and 
partly  to  the  rolling  out  of  the  metal  as  the  bolts  drew 
from  their  sockets  in  the  sheet. 

Lines  of  uniform  extension  seemed  to  be  indicated  by 
a  peculiar  set  of  curved  lines  cutting  the  surface  scale  of 
oxide  on  the  inner  surface  of  each  sheet,  and  resembling 


EXPERIMENTAL  INVESTIGATIONS.  167 

dosely  the  lines  of  magnetic  force  called,  by  physicists, 
magnetic  spectra.  These  curious  markings  surrounded 
all  of  the  stay-bolt  holes. 

The  third  experiment  took  place  on  the  23d  of  No- 
vember. Vhe  boiler  selected  on  this  occasion  was  a 
"return  tubular-boiler,"  with  no  lower  flues  ;  the  furnace 
and  combustion-chamber  occupying  the  whole  lower 
part.  Its  surface  extended  the  whole  width  of  the 
boiler,  thus  giving  an  immense  crown-sheet. 

This  boiler  was  built  in  1845,  and  had  been  at  work 
twenty -five  years ;  when  taken  out,  the  inspector's  cer- 
tificate allowed  30  Ibs.  of  steam.  In  September  it  was 
F'lhiected  to  hydrostatic  pressure,  which  at  42  pounds 
broke  a  brace  in  the  crown-sheet,  and  at  60  pounds,  12 
of  the  braces  over  the  furnace  gave  way,  and  allowed 
so  fiee  an  escape  of  water  as  to  prevent  the  attainment 
of  a  higher  pressure.  The  broken  parts  were  carefully 
repaired,  and  the  boiler  again  tested  at  Sandy  Hook  to 
59  Ibs.,  which  was  borne  without  injury,  and  afterwe&vl 
a  steam-pressure  of  45  Ibs.  left  it  still  uninjured.  At 
the  final  experiment,  the  water  level  was  raised  to  the 
height  of  15  inches  above  the  tubes,  and  it  there 
remained  to  the  end.  The  fire  was  built,  as  in  the  pre- 
vious experiments,  with  as  much  wood  as  would  burn 
freely  in  the  furnace,  and  the  record  of  pressures  was  as 
follows : 


Time. 

12.21    P.M. 

12.23      ' 
a.  25 

Pressure. 

Time. 

Pressure. 

Time. 

Pressure. 

29^  Ibs. 
3373M  " 

12  27  P.M 
12.29     " 
12.31      '• 

41      le* 

44K     " 

48^     " 

12.32  P.M 
12-33      ' 
12-34      ' 

50      Ibs., 
5»        " 
53*    " 

brace  broke; 
exploded. 

1 68  STEAM  BOILER  EXPLOSIONS. 

In  those  second  and  third  experiments,  we  have  illus- 
trations of  the  comparatively  rare  cases  in  which  explo- 
sions actually  occur. 

The  second  was  a  perfectly  new  construction,  in 
which  corrosion  had  not  developed  a  point  of  great 
comparative  weakness,  and  the  edges  yielding  along  the 
lines  of  riveting  on  all  sides  simultaneously  and  very 
equally,  the  two  halves  were  completely  separated,  and 
thrown  far  apart  with  all  of  the  energy  of  unmistakable 
explosion,  although  there  was  an  ample  supply  of  water, 
and  the  pressure  did  not  exceed  that  frequently  reached 
in  locomotives  and  on  the  western  rivers,  and  although 
the  boiler  itself  was  quite  diminutive. 

In  the  third  experiment,  as  in  the  second,  it  is  prob- 
able that  the  weakest  part  extended  very  uniformly  over 
a  large  part  of  the  boiler,  either  in  lines  of  weakened 
metal,  or  over  surfaces  largely  acted  upon  by  corrosion. 
Immediately  upon  the  giving  way  of  its  braces,  frac- 
ture took  place  at  once  in  many  different  parts. 

33.  Conclusion.  We  may  conclude,  then,  from 
the  result  of  Mr.  Stevens'  experiments: 

First. — That  "  low- water,"  although  undoubtedly  one 
cause,  is  not  the  only  cause  of  violent  explosions,  as  is 
so  commonly  supposed,  but  that  a  most  violent  explo- 
sion may  occur  with  a  boiler  well  supplied  with  water, 
and  in  which  the  steam-pressure  is  gradually  and  slowly 
accumulated. 

This  was  shown  on  a  small  scale  by  the  experiments 
of  the  Committee  of  the  Franklin  Institute  above 
referred  to. 


EXPERIMENTAL   INVESTIGATIONS.  169 

Second. — That  what  is  generally  considered  a  moderate 
steam-pressure  may  produce  the  very  violent  explosion 
of  a  weak  boiler,  containing  a  large  body  of  water,  and 
having  all  its  flues  well  covered. 

This  had  never  before  been  directly  proven  by  ex- 
periment. 

Third. — That  a  steam-boiler  may  explode,  under 
steam,  at  a  pressure  less  than  that  which  it  had  success- 
fully withstood  at  the  hydrostatic  test. 

The  last  boiler  had  been  tested  to  59  Ibs.,  and  after- 
ward exploded  at  53^4  Ibs.  This  fact,  too,  although 
frequently  urged  by  some  engineers,  was  generally  dis- 
believed. It  was  here  directly  proven.* 

In  addition  to  the  deductions  summarized  above,  the 
Author  would  conclude : 

Fourth. — That  the  violence  of  an  explosion  under 
gradually  accumulating  pressures  is  determined  largely 
by  the  nature  of  the  injury  and  the  extent  of  the  pri- 
mary rupture  due  to  it.  A  merely  local  defect  or  failure 
would  not  be  likely  to  cause  explosion. 

*  A  number  of  instances  of  this  kind,  though  not  always  producing  an 
explosion,  have  been  made  known  to  the  Author.  Two  boilers  at  the 
Detroit  Water  Works,  in  1850,  after  resisting  the  hydrostatic  test  of 
200  Ibs.  with  water,  at  a  temperature  of  100°  Fahr.,  broke  several  braces 
each  at  no  and  115  Ibs.  steam  pressure  respectively,  when  first  tried 
under  steam.  The  boiler  of  the  U.  S.  steamer  Algonquin  was  tested  with 
1 50  Ibs.  cold  water-pressure,  and  broke  a  brace  at  100  Ibs.  when  tried 
with  steam.  A  similar  case  occurred  in  New  York,  a  few  years  ago,  and 
the  boiler  exploded  with  fatal  results.  These  accidents  are  probably 
caused  by  the  changes  of  form  of  the  boiler,  under  varying  temperature, 
which  throw  undue  strain  upon  some  one  part,  which  may  have  already 
been  nearly  fractured. 


170 


STEAM  BOILER  EXPLOSIONS. 


Fifth. — That  the  overheating  of  the  metal  of  a  boiler 
in  consequence  of  low-water  may,  or  may  not,  produce 
explosion,  accordingly  as  the  sheet  is  more  or  less 
weakened,  or  as  the  amount  of  steam  made  on  the  over- 
flow of  the  dry  heated  area  by  water  is  greater  or  less. 

Sixth. — That  the  superheating  of  either  water  or 
steam  is  not  to  be  considered  a  probable  cause  of  ex- 
plosion. 

Seventh. — That  the  question  whether  the  repulsion  of 
water  from  a  plate  by  the  overheating  of  the  latter  may 
occur  with  resulting  explosion  remains  unsettled,  but 
that  it  is  certain  that  the  number  of  explosions  attrib- 
utable to  this  cause  is  comparatively  small. 

Eighth. — That  all  explosions  are  certainly  due  to 
simple  and  preventable  causes,  and  nearly  all  to  simple 
ignorance  or  carelessness,  on  the  part  of  either  designer, 
constructor,  proprietor,  or  attendants. 

A  Committee  of  the  British  House  of  Commons 
after  long  study  and  careful  investigation  of  this  subject, 
made  the  following  recommendations  : 

"  13.  (a)  That  it  be  distinctly  laid  down  by  statute 
that  the  steam-user  is  responsible  for  the  efficiency  of 
his  boilers  and  machinery,  and  for  employing  competent 
men  to  work  them ;  (b)  that,  in  the  event  of  an  explo- 
sion, the  onus  of  proof  of  efficiency  should  rest  on  the 
steao-user  ;  (c)  that  in  order  to  raise  prima  facie  proof, 
it  shall  be  sufficient  to  show  that  the  boiler  was  at  the 
time  of  the  explosion  under  the  management  of  the 
owner  or  user,  or  his  servant,  and  such  prima  facie 
proof  shall  only  be  rebutted  by  proof  that  the  accident 


EXPERIMENTAL  INVESTIGATIONS,  17  r 

arose  from  some  cause  beyond  the  control  of  such 
owner  or  user ;  and  that  it  shall  be  no  defence  in  an 
action  by  a  servant  against  such  owner  or  user  being  his 
master,  that  the  damage  arose  from  the  negligence  of  a 
fellow  servant." 

The  Prevention  of  steam-boiler  explosions  is  now 
seen  to  be  a  matter  of  the  utmost  simplicity.  A  well 
designed,  well  made  and  set,  and  properly  managed 
steam-boiler  may  be  considered  as  safe.  Explosions 
rarely  occur  in  such  cases.  To  secure  correct  design 
and  proportions,  a  competent  engineer  should  be  found 
to  make  the  plans;  to  obtain  good  construction,  a  reli- 
able, intelligent  and  experienced  maker  must  be  entrusted 
with  the  construction  under  proper  supervision  and  pre- 
cise instructions  from  the  designer ;  and  the  latter  should 
also  attend  carefully  to  the  installation  of  the  boiler. 
In  order  to  insure  good  management,  trustworthy,  skill- 
ful, and  experienced  attendants  must  be  found,  who, 
under  definite  instructions,  may  at  all  times  be  depended 
upon  to  do  their  work  properly.  Periodical  inspection, 
prompt  repair  of  all  defects  when  discovered,  and  the 
removal  of  the  boiler  before  it  has  become  generally 
deteriorated  and  unreliable,  are  the  best  safeguards 
against  explosion. 

This  inspection  should  be  made  by,  or  in  accordance 
with,  the  best  methods  of  reputable  insurance  and  in- 
spection companies,  by  an  expert  of  recognized  com- 
petence and  experience.  It  should  include  both  inter- 
nal and  external  inspection  of  every  part  and  no  part 


STEAM  BOILER   EXPLOSIONS. 


should  be  permitted  to  be  inaccessible  for  such  inspec- 
tion. If  such  part  is  thus  necessarily  neglected,  it  may 
reasonably  be  expected  that  a  catastrophe  may  have 
origin  at  that  point. 

This  inspection  should  be  accompanied  by  "ham- 
mer-test" of  parts  known  to  be  liable  to  deterioration 
and  should  usually  be  followed  by  a  test  under 
hydraulic  pressure  to  determine  the  safety  of  the 
structure  as  a  whole.  The  concealed  laps  of  shell- 
boiler  seams  and  the  stays  of  locomotive  boilers  are 
peculiarly  liable  to  failure,  and  should  therefore  be 
most  carefully  watched. 

Wrought  iron  has  now  been  practically  superseded 
by  steel  in  boiler-work,  and  the  homogeneousness  and 
reliability  of  the  metal  add  greatly  to  the  security  of 
the  structure. 

The  following  are  comparative  records  of  railroad 
accidents  and  boiler  explosions.* 

RAILWAY  ACCIDENTS,  JAN.,  FEB.,  AND  MARCH,  1902. 


Character  of 
Accidents, 

Number  of 
Accidents. 

Passengers. 

Employe's. 

Killed. 

Injured. 

Killed. 

Injured. 

Collisions      

I,22O 
838 

26 
15 

501 
298 

104 

53 

763 
351 

Derailments  
Totals   ...  . 

2,058 

41 

799 

J57 

1,114 

*  The  Locomotive,  August,  1902. 


EXPERIMEN  TA  L    IN  VES  TIG  A  TIOXS.  1 7  3 

BOILER  EXPLOSIONS,  JAN.,  FEB.,  AND  MARCH,  1902. 


Month. 

Number  of 
Explosions. 

Persons 
Killed. 

Persons 
Injured. 

7C 

25 

45 

^8 

24 

46 

March          ... 

32 

22 

32 

Totals         

IOS 

71 

121 

The  very  common  form  of  explosion,  especially 
with  locomotives,  due  to  low  water  and  over-heated 
crown-sheets,  may  be  avoided  usually  by  proper  use 


FIG.  63. — DRILLED  STAYBOLT. 

of  good  forms  of  fusible  plugs.  Their  liability  to 
failure  to  act  when  covered  by  incrustation  or  sediment 
may  be  reduced  by  proper  inspection  and  care.  They 


174  STEAM  BOILER  EXPLOSIONS. 

should  be  renewed  at  intervals,  as  they  are  sometimes 
altered  by  long  exposure  to  heat  and  rapid  changes  of 
temperature. 

Staybolts  should  be  similarly  treated,  renewing  a 
portion  at  each  inspection  in  such  manner  that  none 
should  be  retained  longer  than  about  two  years.  Solid 
staybolts  should  be  drilled  axially  to  insure  detection  of 
faults  before  breakage  takes  place.  "Flexible  stay- 
bolts"  are  probably  safest.  The  corrugated  furnace 
evades  this  danger. 

In  construction,  expansion  and  contraction  should 
be  carefully  provided  for.  Bent  sheets  should  have 
large  radii  of  curvature. 

A  factor  of  safety  vtfive  is  usually  prescribed;  but  a 
larger  figure  will  decrease  danger  initially  and  will 
prolong  the  working  period. 

Solid-drawn  tubes  can  now  be  obtained  for  boilers, 
and  are  vastly  preferable  to  lap-welded  tubes. 

In  water-tube  boilers  particularly,  thicker  tubes  are 
coming  into  use. 

Danger  from  the  presence  of  oil  can  only  be  evaded 
by  its  exclusion  from  the  boiler.  Alkalies  in  solution 
prevent  corrosion. 

Acid  oils  should  never  enter  a  boiler.  The  only 
other  source  of  corrosion  is  air  in  the  feed-water,  and 
since  the  substitution  of  mineral  for  animal  lubricating 
oils,  this  is  the  only  cause  of  the  "  pitting  "  often  occur- 
ring in  all  boilers,  and  especially  in  water-tube  boilers. 
Alkaline  water  produces  little  or  no  corrosion  in  any 
case.  Acid  water  may  cause  exceedingly  serious  injury. 


EXPERIMENT  A  L   IN  VES  TIG  A  TIONS.  1 7  5 

Sea-water  is  ordinarily  about  twice  as  corrosive  as  pure 
water,  and  added  mineral  matter,  as  chlorides  and  sul- 
phates, has  greater  effect  in  solution  than  with  pure 
water. 

Mr.  F.  J.  Rowan,  after  a  very  extended  review  of 
the  subject,  sums  up  the  case  for  prevention  of  destruc- 
tion of  boilers,  especially  marine,  by  explosion  or 
otherwise,  thus : 

1.  The  metal  of  which  boilers  are  constructed  should 
be   as  homogeneous   as   possible   in   composition    and 
texture.     It  should  be  well  worked,  so  as  to  be  fibrou3 
rather  than  crystalline  in  texture,  and   should  not  be 
punched  or  worked  at  a  low  heat.     It  should  be  well 
annealed,  so  as  to  remove  all  effects  of  local  stresses, 
and  to  bring  the  texture  to  a  uniform  condition. 

2.  All  mill  scale  and  dirt  should   be   removed  from 
the  surfaces,  which  should  also  be  kept  as  free  as  pos- 
sible from  oil. 

3.  All  gases  should  be  removed  from  the  water. 

4.  No  sea-water  should  be  admitted,  and   all   feed- 
water  should  be  made  up  with  distilled  water. 

5.  All  feed- water  should  be  passed  through  a  good 
filter. 

6.  The  feed-water  should  be  heated  in  feed-heaters 
which  are  separate  in  construction  from  the  boiler. 

7.  The    interior    surfaces    of  the    boiler    should  be 
covered  by    a    thin   protective   coating   or    the   water 
should  be  treated  chemically. 

8.  No  vegetable  or  animal  i»il  should  be  used  in  any 
engines  connected  in  any  way  with  the  boiler. 

9.  When  not  in  use  boilers  should  be  carefully  pro- 
tected from  deterioration. 


176 


STEAM  BOILER   EXPLOSIONS. 


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INDEX. 


ART.  PAGE 

BOILERS, 

energy  stored  in ,....     7  23 

explosions,  statistics  of : n  41 

management  of ...  29  125 

relative  safety  of 22  9? 

BURSTING,  explosion  distinguished  from 9  3 

CALCULATIONS  OF  ENERGY;  deductions  from 4  12 

CAUSES  OF  EXPLOSIONS 10  36 

COLBURN  AND  CLARK'S  THEORY  OF  EXPLOSIONS 13  49 

CONCLUSIONS;  preventives  of  explosions 33  168 

CONSTRUCTIONS;  defective .24  105 

CURVES  OF  ENERGY 5  15 

DECAY,  general  and  local 26  114 

methods  of 27  117 

DESIGN,  defective 23  100 

EMERGENCIES 30 

ENERGY, 

calculated  quantity  of 3  8 

character  of 6  17 

curves  of 5  15 

deductions  from  calculations  of 4  12 

formulas  for  stored 2  4 

in  heated  metal 15  61 

in  super-heated  water 19  78 

of  steam  alone 8  32 

stored  in  steam  boilers 7  23 

stored,  of  fluid I  3 

177 


178  INDEX. 

EXPLOSIONS, 

causes  of 10  36 

distinguished  from  bursting 9  34 

experimental  investigations  of 32  1 56 

preventives  of 33  168 

results  of 3  41 

statistics  of  boiler n  3 

FLUID,  stored  energy  of 2  3 

FORMULAS,  for  energy  stored 2  4 

INCRUSTATION,  sediment  and , 18  73 

INVESTIGATION,  experimental 32  156 

Low  WATER  AND  CONSEQUENCES 17  63 

MANAGEMENT  OF  BOILERS 29  125 

METAL, 

energy  in  heated 15  61 

resistance  of  heated 16  63 

METHODS,  theories  and,  of  explosions. 12  47 

PRESSURE,  steady  increase  of 21  94 

PREVENTIVES  OF  EXPLOSIONS 33  168 

SAFETY,  relative,  of  boilers 22  98 

SEDIMENT  AND  INCRUSTATIONS 18  73 

SPHEROIDAL  STATE  OF  WATER 20  86 

STATISTICS  OF  BOILER  EXPLOSIONS n  41 

STEAM  ALONE,  energy  of „....     8  122 

TEMPERATURE  CHANGES 28  122 

THEORY,  Colburn  and  Clark's 13  49 

THEORIES  AND  METHODS  OF  EXPLOSIONS 12  47 

WATER, 

energy  in  super-heated 19  78 

low,  and  its  effects .,., ...e,  17  63 


spheroidal  state  of „ . . .  20 


WEAKNESS,  developed 25       ico 


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7 


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"       Elements  of  Analytical  Mechanics 8vo,  3  00 

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Kneass's  Practice  and  Theory  of  the  Injector 8vo,  1  60 

MacCord's    Slide-valves 8vo,  2  00 

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Du  Bois's  Elementary  Principles  of  Mechanics: 

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Du  Bois's  Mechanics  of  Engineering.    Vol.  I Small  4to,  7  50 

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Durley's  Elementary  Text-book  of  the  Kinematics  of  Machines. 

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Holly's  Art  of  Saw  Filing 18mo,  75 

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Kerr's  Power  and  Power  Transmission 8vo,  2  00 

Lanza's  Applied  Mechanics 8vo,  7  60 

MacCord's  Kinematics;  or,  Practical  Mechanism 8vo,  5  00 

"          Velocity   Diagrams 8vo,  1  50 

Merriman's  Text-book  on  the  Mechanics  of  Materials 8vo,  4  00 

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14 


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Cloth,  1  26 

Dictionary  of  the  Names  of  Minerals 8vo,  3  60 

Dana's  System  of  Mineralogy Large  8vo,  half  leather,  12  60 

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"      Minerals  and  How  to  Study  Them 12mo,  1  50 

*      Catalogue  of  American  Localities  of  Minerals. Large  8vo,  1  00 

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Hussak's     The     Determination     of     Rock-forming     Minerals. 

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Rosenbuach's  Microscopical  Physiography  of  the  Rock-making 

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Williams's  Manual  of  Lithology 8vo,  3  00 


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O'DriscolPs  Notes  on  the  Treatment  of  Gold  Ores 8vo,  2  00 

Sawyer's  Accidents  in  Mines 8vo,  7  00 

Walke's  Lectures  on  Explosives 8vo,  4  00 

Wilson's  Cyanide  Processes 12mo,  1  60 

Wilson's  Chlorination  Process 12mo,  1  60 

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SANITABY  SCIENCE. 

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Fuertes's  Water  and  Public  Health 12mo,  1  60 

"        Water-filtration   Works 12mo,  260 

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Merriman's  Elements  of  Sanitary  Engineering 8vo,  2  00 

Nichols's  Water-supply.     (Considered  Mainly  from  a  Chemical 

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Ogden's  Sewer  Design 12mo,  2  00 

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Richards's  Cost  of  Food.    A  Study  in  Dietaries 12mo,  1  00 

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16 


UNIVERSITY  OF  CALIFORNIA  LIBRARY, 
BERKELEY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

Books  not  returned  on  time  are  subject  to  a  fine  of 
50c  per  volume  after  the  third  day  overdue,  increasing 
to  $1.00  per  volume  after  the  sixth  day.  Books  not  in 
demand  may  be  renewed  if  application  is  made  before 
expiration  of  loan  period. 


APR  24  1925 


»>!• 


JANS 


15m- 12, '2- 


-:; 


